Geometric crystalography

Geometric Crystalography

Geometric Crystalography

Contents Introduction

1

Isometric

3

Tetragonal

9

Orthorhombic

15

Hexagonal

19

Trigonal

25

Monoclinic

31

Triclinic

35

Introduction Geometric Crystalography is a classification of minerals based off of their crystal formation. As chemical compounds change from a liquid or gas to a solid, they take on a polyhedral form bounded by smooth faces. These forms are categorized, by their geometry, into six Systems: Isometric Tetragonal Orthorhombic Hexagonal Trigonal Monoclinic Triclinic Each of these Systems are subdivided into a total of 32 Classes based on different planes of symmetry within the crystalline form. The geometry and symmetry of the systems can be defined through Crystallographic Axes. These axis work on a threedimensional plane to show the angles and differing lengths of the faces of the forms. Each axis is labeled with a positive and negative side to represent one side coming forward and the other receding. The point where all axis meet is called the axial cross.

c Axial Cross

-b

a

-a b

-c

This book will proceed to describe and catalog the crystal Systems and Classes.

1

Isometric

2

have the highest degree of SYMMETRY, w compared to all the other crystal syste Did you know that there is only ONE obj in the geometrical universe with perf symmetry? Infinite planes of symmetry p through its center, infinite rotatio axes are present, and no matter how lit or much you rotate it on any of its infin number of axes, it appears the same sphere. No crystal system even approaches a spher degree of symmetry, but the isometric sys is often quickly recognizable because s of the forms and combinations of fo somewhat approach sphericity (or, at lea roundness), especially when the faces be to be curved, due to the high degree symmetry in the isometric system. Let’s begin by looking at the Herma Mauguin notation for the first se isometric forms and each form’s notatio Cube {001} Dodecahedron {011} Trapezohedron {hhl} Hexoctahedron {h Octahedron {111} Tetrahexahed {0kl} Trisoctahedronv {hll} For these forms, the 3 crystallograp axes are axes of 4-fold rotation. Th are also 4 diagonal axes of 3-fold rot inversion that pass through the form at point where the cube’s 3 faces would jo Furthermore, there are 6 directions 2-fold symmetry (at the center of the l formed by the intersection of 2 plane There is also a center of symmetry. Th are 9 mirror planes. This combination symmetry elements defines the high possible symmetry of crystals. So Hermann-Mauguin notation is 4/m-32/m. In a textbook, my notation (-3) is presen as the number 3 with a negative sign ab it, but due to computers and web browser can’t place this special notation prope in cyberspace, so don’t get confused if look this up in a mineralogy book! It sho be pronounced as “negative 3” or “bar In this instance, the -3 is the notat for the 3-fold axis of rotary inversi I will consistently use the negative s before the number when it is necessa The same stands true for my notation w 5 Classes: dealing with Miller indices or general f notation. Tetartoidal Crystallographers group forms by th symmetry notation, the first seven we w Diploidal consider have the same symmetry - 4/m-32 CUBE-- The cube is composed of 6 square fa Gyroidal at 90 degree angles to each other. E face intersects one of the crystallograp axes and is parallel to the other t Hextetrahedral This form, {001}, is one of the easi to recognize and many minerals display with little modification. Think of gale Hexoctahedral pyrite, fluorite, perovskite, or hal cubes! OCTAHEDRON-- The octahedron is a f composed of 8 equilateral triangles. Th triangle-shaped faces intersect all crystallographic axes at the same distan thus the form notation of {111}. Miner commonly3 exhibiting the simple octahed Axial Configuration: form are magnetite, chromite, franklini spinel, pyrochlore, cuprite, gold, 1 diamond. Sometimes fluorite, pyrite, The three axes titled a , galena take this form. 1 2 3 DODECAHEDRON (AKA Rhombic Dodecahedron) a and a are all equal in This form is composed of 12 rhomb-sha Each of these rhomb-shaped fa intersects two of 2faces. 2 the axes at equidista length and intersect at and is parallel to the 3rd axis, thus notation {011}. The different mine species of the garnet group often disp 90° to each other. this 1 form. Magnetite and sodalite someti exhibit this form. 3.5 3.6 TETRAHEXAHEDRON-- This form has 24 isoce triangular faces. The easiest way 3 its understand shape is to envision cube that on each face has 4 equal-si triangular faces that have been rai from the center of the cube face. E triangular face has its base attached the edge of the cube and the apex of two equal-length sides rises to meet 4-fold axis. Because of the variation inclination to this axis, there exist 29 minerals from unknown or uncertain class: number of possible tetrahexahedral for but all meet the general notation of {0h The most common form is {012}. It Alumotungstite Danbaite Kimrobinsonite Walfordite interesting to note that as the combinat each Yttrocerite set of 4 faces rise along the ax Amalgam Gutsevichite Kobeite-(Y)of this form approaches the dodecahedron. they fall, the form approaches a cube. Antitaenite Hemusite Kurilite Zaratite tetrahexahedron is rarely the domin Bilibinskite Henryite Mcalpineite form on natural crystals, instead be to the cube, octahedron Blakeite Horsfordite Sakuraiite subordinant dodecahedron. Cubic minerals on wh you may sometimes see this form exhibi Calvertite Iridisite Sreinite include fluorite (cube and tetrahexahedro Cervelleite Isochalcopyrite Telargpalite magnetite or copper (octahedron and garnet (dodecahed Choloalite Kiddcreekite Tongxinite tetrahexahedron) and tetrahexahedron).

The Isometric (Cubic) System

a

-a a

-a a

-a

3

TRAPEZOHEDRON (AKA Tetragon-trioctahedr -- This form has 24 similar trapezi shaped faces. If my Webster’s is corre a trapezium is a 4-sided plane that no sides parallel. Each of these fa intersects a crystallographic axis a unit distance and the other two axes equal distances, but those intersecti

Tetartoidal

25 minerals from the Tetartoidal Class: Brownleeite Changchengite Corderoite Efremovite Fersilicite Gersdorffite Hsianghualite

Kuznetsovite Langbeinite Maghemite Manganolangbeinite Maslovite Melliniite Michenerite

Milotaite Nabaphite Nastrophite Nitrobarite Padmaite Pahasapaite Sillenite

Diploidal

59 minerals from the Diploidal Class:

4

Alum-(K) Alum-(Na) Aurostibite Avicennite Bixbyite Bravoite Cafarsite Cattierite Chukhrovite-(Ce) Chukhrovite-(Nd) Chukhrovite-(Y) Cliffordite Dzhalindite Dzharkenite Dzhezkazganite

Erlichmanite Ertixiite Ferroskutterudite Ferrotychite Fukuchilite Gaotaiite Geversite Griphite Hauerite Hollingworthite IMA2008-067 Insizwaite Irarsite Jolliffeite Kalungaite

Kieftite Krutaite Krutovite Lanmuchangite Laurite Lonecreekite Manganotychite Mayingite Menezesite Meniaylovite Miessiite Nabiasite Nickelskutterudite Northupite Penroseite

used. The most common mineral form is and leucite, usually crystallize as si uncommon, varying from dominant to sub where it is often combined with the dod TRISOCTAHEDRON (AKA Trigonal Trisoctahe but the faces are isoceles triangles. Ea axes at unity, and the third axes at s notation in general of {hll}. To more easily visualize what a triso an octahedron. Each octahedral face is drawing 3 lines, each originating at reaching the 3 corners of that face. Rep faces on an octahedron and you have a t trisoctahedron is scarce, most commonl as a subordinant form. It has recently been demonstrated tha not a true crystal form (true crystal a solution form caused by the differen during its transport from the mantle t altogether! As a subordinant form, it the octahedron for fluorite and magnet octahedron on complex crystals of galen HEXOCTAHEDRON-- This form has 48 trian raised from each face of a simple oc drawing a line from the center of each through the face center to the opposite 7 faces of an octahedron and you have a Just like the trisoctahedral form, thi where it is thought to represent a sol not true crystallization. With both the often curved, resulting in a near spheri dodecahedron and subordinant hexoctahed TETRAHEDRON-- The tetrahedron includes the notation {111} and {1-11}, respecti one another. A tetrahedron is a 4-face triangle. Each face intersects all 3 crystallogr may derive this form from an octahedr they meet (this also shrinks the oppos Testibiopalladite disappear). Tolovkite If both positive and negative forms then the initial appearance of the cr Ullmannite an octahedron. Here is where the diff Willyamite features become exceedingly important i has this crystal form that the minera tetrahedrite. Other examples are diamon TRISTETRAHEDRON-- By now, I think you mi examples how to derive this form. Yep, t triangle-shaped faces on each of the 4 triangular faces3.16Just like the tetr negative forms, designated as {hhl} an relatively common form on tetrahedrite, but has also been reported on sphaleri being present on diamond can’t be overl result of solution processes, rather th HEXTETRAHEDRON-- Again, we take a tetr hexoctahedron, we raise 6 triangular center of the equilateral triangular f on the entire tetrahedron results in negative forms, designated as {hkl} an been reported on tetrahedrite, but r solution form on diamond. DELTOID DODECAHEDRON-- This is a 12-fac faces on the each face of a tetrahedron faces are rhombic. There are both posi {hll} and {h-ll}, respectively. This fo one on tetrahedrite or sphalerite, wher faces modifying the corners of the domi Now we have only 4 remaining forms to first to consider is the gyroid. 3.19GYROID (Pentagon-trioctahedron)-The Hermann-Mauguin notation is 432. Th left-handed symmetry. Older mineral tex sometimes reported on cuprite. But most r of cuprite’s crystallography showed cup this is so, then we have no natural min although some laboratory-grown crystals Two of the 3 remaining forms have 3 2inversion axes, and 3 of the axial pla Hermann-Mauguin notation is 2/m-3. The and the diploid. PYRITOHEDRON (Pentagonal dodecahedron)of which intersects one crystallograph axis at some multiple of unity, and is positive and negative forms, designat There are a number of pyritohedral f inclination of the faces. The most comm Platarsite (fig. 3.20). Pyrite is the only common Pyrite often subordinate, combining with the c Rondorfite DIPLOID (Didodecahedron)-- There are 24 Schoenfliesite half of the faces of a hexoctahedron. T figures 3.20 and 3.21. The diploid loo Skutterudite are made from each pentagonal face of Sohngeite are trapezia. There are both positive a and {khl}, respectively. Pyrite is the Sperrylite diploid form. Crystal forms in the isom Trogtalite SYMMETRY, when compared to all the oth Tschermigite there is only ONE object in the geomet Infinite planes of symmetry pass throug Tychite are present, and no matter how little Vaesite infinite number of axes, it appears the No crystal system even approaches a Villamaninite isometric system is often quickly recog Winstanleyite combinations of forms somewhat approach especially when the faces begin to b Yttropyrochlore-(Y) symmetry in the isometric system. Let’s begin by looking at the Hermann isometric forms and each form’s notatio Cube {001} Dodecahedron {011} T {hkl} Octahedron {111} Tetrahexahedron For these forms, the 3 crystallograph There are also 4 diagonal axes of 3-fo

{112}. Two silicate minerals, analcime imple trapezohedrons. This form is not bordinate, on many varieties of garnet, decahedron. edron ) -- This is another 24-faced form, ach face intersects two crystallographic some multiple of unity; hence the form

Gyroidal

octahedron looks like, first think of s divided into 3 isoceles triangles by the center of the octahedral face and peat this operation for the remaining 7 trisoctahedron. As a dominant form, the ly being reported for diamond, usually at trisoctahedral diamond is probably l forms are growth forms), but instead ntial dissolving of octahedral diamond to the crust, but that’s another story has been reported in combination with tite and in combination with cube and na. ngular faces, 6 faces appearing to be ctahedron. These may be envisioned by of the 3 edges of an octahedral face, e corner. Repeat this for the remaining a hexoctahedron. is form is most often seen on diamond, lution form derived from an octahedron, e tris- and hexoctahedron, the faces are ical shape. The combination of dominant dron is not uncommon for garnet. both a positive and negative form with ively. These are simple mirror images of ed form, each face being an equilateral

raphic axes at the same distance. You 4 minerals ron by extending alternate faces until sing set of alternate faces Fischesserite until they

from the Gyroidal Class:

Petzite are equal sized on a single crystal, rystal form is INDISTINGUISHABLE Sakhaite from ferences in and orientation Yeelimite of surface in form study. One mineral so commonly al was named after the form itself nd, helvite, and sphalerite. ight be able to tell me from my previous take a tetrahedron and raise 3 isoceles tetrahedral faces. So this form has 12 rahedron, there are both positive and nd {h-hl}, respectively.This is only a usually subordinant to the tetrahedron, ite and boracite. The possibility of it looked, but as mentioned, it may be the han crystallization. rahedron and, in similar manner as the faces having a common apex from the face of the tetrahedron. Repeating this 24 faces. There are both positive and nd {h-kl}, respectively. This form has rarely on sphalerite. Also a possible

Hextetrahedral

ced form, derived by raising 3 4-sided (fig. 3.18). The shape of the resultant itive and negative forms, designated as orm is sometimes seen as a subordinate re it would appear as a set of 3 rhombic inant tetrahedral shape. o discuss in the isometric system. The

This form has no center of symmetry! here are two forms, based on right- and xtbooks state that this is a rare form, recent textbooks indicate that a restudy prite to probably be hexoctahedral. If neral that crystallizes with this form, s with this form are known. -fold rotational axes, 4 3-fold rotary 66 minerals anes are mirror planes of symmetry. The ese forms consist of the pyritohedron

Alumopharmacosiderite each -- There are 12 pentagonal faces, hic axis at unity, intersects a second s parallel to the third axis.Argentotennantite There are ted as {h0l} and {0kl}, respectively. Arsenosulvanite forms, differing due to the degree of Barium-alumopharmon form is the {102}, the positive form mineral that displays this form. It is macosiderite cube, diploid (below), or octahedron.] Bicchulite 4 faces, each face corresponding to oneChameanite This is a rare form. You should compare oks like a pyritohedron whereColoradoite two faces the pyritohedron. The resulting faces and negative forms, designated as {hkl} Colusite only common mineral that exhibits the metric system have the highestDanalite degree of her crystal systems. Did you Dansite know that trical universe with perfect symmetry? gh its center, infinite rotational axes Dienerite e or much you rotate it on any of its Domeykite e same! A sphere. sphere’s degree of symmetry, but the gnizable because some of theEugenite forms and h sphericity (or, at least, roundness), be curved, due to the high Eulytite degree of Freibergite

n-Mauguin notation for the first seven on: Trapezohedron {hhl} Hexoctahedron {0kl} Trisoctahedronv {hll} hic axes are axes of 4-fold rotation. old rotary inversion that pass through

from the Hextrahedral Class: Galkhaite Gananite Genthelvite Germanite Germanocolusite Gianellaite Giraudite Goldfieldite Hakite Hauyne Hawleyite Helvite Ivanyukite-Cu Ivanyukite-K Ivanyukite-Na Kolymite Lazurite

Londonite Maikainite Marshite Mayenite Metaborite Metacinnabar Miersite Mosesite Murataite Nantokite Natropharmacosiderite Nekrasovite Nosean Ovamboite Panichiite Pharmacosiderite Phosphovanadylite

Putzite Rhodizite Roaldite Rudashevskyite Sodalite Sphalerite Stibiocolusite Stilleite Sulvanite Talnakhite Tarkianite Tennantite Tetrahedrite Tiemannite Vasilite I Wadalite Zunyite

5

Hexoctahedral

244 minerals from the Hexoctahedral Class:

6

Alabandite Almandine Altaite Aluminum Andradite Argentite Argentopentlandite Arsenolite Asselbornite Atokite Auricupride Awaruite Bariopyrochlore Berzelianite Berzeliite Betafite Bideauxite Bindheimite Bismutomicrolite Bismutopyrochlore Bismutostibiconite Bogdanovite Boleite Bornhardtite Borovskite Bromargyrite Brunogeierite Bunsenite Cadmoindite Calciobetafite Calderite Carlsbergite Carobbiite Carrollite Cerianite-(Ce) Ceriopyrochlore-(Ce Cesstibtantite Chengdeite Chlorargyrite Chromferide Chromite Chromium Clausthalite Cobaltpentlandite Cochromite Copper Coulsonite Cryolithionite Cryptohalite Cuboargyrite Cuprite Cuproiridsite Cuprorhodsite Cuprospinel Damiaoite

Daubreelite Dayingite Diamond Djerfisherite Eglestonite Elpasolite Embolite Faujasite-Ca Faujasite-Mg Faujasite-Na Ferchromide Ferritungstite Ferrorhodsite Fletcherite Florensovite Fluorite Fluornatromicrolite Frankdicksonite Franklinite Gahnite Galaxite Galena Geffroyite Gold Goldamalgam Goldmanite Greigite Griceite Grossular Gupeiite Haleniusite-(La) Halite Hapkeite Haxonite Hercynite Hibschite Hieratite Hongquiite Hunchunite Hydrougrandite IMA2009-014 Indite Iridium Iron Isocubanite Isoferroplatinum Isolueshite Isomertieite Isovite Jacobsite Jixianite Kadyrelite Kalininite Kalipyrochlore Kamacite

Katoite Keilite Khamrabaevite Kimzeyite Knorringite Kutinaite Lafossaite Lead Lesukite Lewisite Lime Linnaeite Loparite-(Ce) Magnesiochromite Magnesiocoulsonite Magnesioferrite Magnetite Magnussonite Majorite Malanite Maldonite Manganberzeliite Manganochromite Manganoshadlunite Manganosite Melanophlogitebta Methane hydrate-I Methane hydrate-II Mgriite Miassite Microlite Monimolite Monsmedite Monteponite Morimotoite Morozeviczite Moschellandsbergite Murdochite Mushistonite Natanite Natrobistantite Natrophosphate Nichromite Nickel Niningerite Niobocarbide Oldhamite Osbornite Owensite Palenzonaite Palladium Palladseite Partzite Paulingite-Ca Paulingite-K

Paulingite-Na Pentlandite Periclase Platinum Plumbobetafite Plumbomicrolite Plumbopyrochlore Polkovicite Pollucite Polydymite Prassoite Putoranite Pyrochlore Pyrope Qandilite Ralstonite Rhodium Ringwoodite Romeite Rustenburgite Salammoniac Schaferite Schapbachite Schorlomite Senarmontite Shadlunite Siegenite Silicon Silver Skaergaardite Spessartine Spinel Stannomicrolite Stetefeldtite Stibiconite Stibiobetafite Stibiomicrolite Strontiopyrochlore Suessite Sulphohalite Sylvite Taenite Tantalcarbide Tantalum Tausonite Tazheranite Thalfenisite Thorianite Trevorite Trustedtite Tschortnerite Tyrrellite Ulvospinel Uraninite +

7

Tetragonal

Our discussion of the TETRAGONAL SYSTEM starts by examining the tetragonal axial cross and comparing it to the isometric axial cross. Remember that in the isometric system all 3 axes were the same length and at right angles to each other. In the tetragonal system, we retain the same angular relationships, but vary the length of the vertical axis, allowing it to be either longer or shorter than the other two. We then relabel the vertical axis as c, retaining the same positive and negative orientation of this axis. As to the Hermann-Mauguin notation for the tetragonal system, the first part of the notation refers to the c axis and the second or third parts refer to the a1 and a2 axes and diagonal symmetry elements, in that order. The tetragonal prism and pyramid forms have the symmetry notation 4/m2/ m2/m. First, I want to consider the tetragonal prisms. There are 3 of these open forms consisting of the 1st order, 2nd order, and ditetragonal prisms. Because hey are not closed forms, in our

igures we will add a simple pinacoid ermination, designated as c. The inacoid form intersects only the c xis, so its Miller indices notation s. It is a simple open 2-faced form.

he first order prism is a form having faces that are parallel to the c axis nd having each face intersect the 1 and a2 axes at the same distance unity). These faces are designated y the letter m and the form symbol s {110}. The second order prism is ssentially identical to the first rder prism, but rotated about the c xis to where the faces are parallel o one of the a axes, thus being erpendicular to the other a axis. The aces of the second order prism are esignated as a and their form symbol s {100}. t becomes apparent that the faces of oth prisms are identical, and their etter designation is only dependent n how they are oriented to the two

a axes. When these forms are combined, then you may readily see their relationships, one to the other. If each form is equally developed, the result is an eight-sided prism. In this instance, we must remember that this apparent shape is the combination of two distinct forms. The third prism form is the ditetragonal prism. It may easily be confused with the combination form of the first and second order prisms, especially if they are equally developed. But compare the orientation of the ditetragonal prism to the a axes in relation to the combination form. What you should do is envision8 looking down the c axis of the ditetragonal prism and the combined 1st and 2nd order tetragonal prisms, then you will see the similarity.

combined prism forms, and with natural malformations, could b indistinguishable one from th other. When examining a natural crystal surface, features, suc as orientation of striations growth or etch pits, may b different on the two prisms of the combined form, whereas with the ditetragonal prism all these features will have the same orientation. The ditetragonal prism has the symbol (hk0). The blue lines indicating the axes are projected additionall on the top and bottom of this shaded drawing, so you can understand the perspective of this eight sided “stop sign” form. Another for in the tetragonal system is the dipyramid and -- yes, you guessed it -- there are 3 types of dipyramids. They correspon to the three types of prisms just described. The name dipyrami is given to a closed form whose plane intersects all three axes (this is true in all crystal systems but the isometric). We do not allow this form to intersect the c axis at the same length as the a axes, because we already defined that form a an octahedron in the isometric system. So it can intersect at either a longer or shorter distance along the c axis than the length of the a axes. Note the orientation to the axial cross (fig. 4.4, the common {111} form). We designat the faces of the first order dipyramid as p. The second order dipyramid has the basic shape as the form of the first order dipyramid, differing onl in its orientation to the axia cross (fig. 4.5, the common {011} form). The second order dipyramid faces are designate by the letter e. Zircon is 1a wonderful mineral to observe both the tetragonal dipyramid and tetragonal pris on. In fact, you might 2 faces be surprised2 at the variation of the length of the c axis i zircon crystals from differen 1 localities. Zircon may var from short stocky nearl equidimensional crystals to almost acicular and have the same basic forms. Before we discuss the 3rd dipyramid form, you nee to look at the various drawing in Figure 4.6 to realize the variety of what may be produce by combining these simpl tetragonal or uncertain class: forms. In figur 4.6c, the faces designated as u represent another 1st order dipyramid with a differen Sinjarite angle of intersection with the Sphaerobismoite vertical axis. Volfsonite Woodruffite Now to the 3rd dipyramid form, the ditetragonal dipyramid. Yecoraite Zapatalite Yes, it’s a closed termination form having 16 faces. Think of this form as a double 8-sided pyramid whose 16 similar faces meet the 3 axes at un9 equal distances. The general symbol is {hkl}. This form is rarely dominant, but is common enough as a subordinant form on zircon to be nicknamed a zirconoid. Anatase may also

The Tetragonal System 7 Classes: Disphenoidal Pyramidal Dipyramidal Scalenohedral Ditetragonal Pyramidal Trapezohedral Ditetragonal Dipyramidal Axial Configuration: Three axes all intersecting at 90° angles. Axes a1and a2 are equal in length. Axis c is either shorter or longer in length.

c

-a a

-a a

-c

22 minerals from unknown Benleonardite Cesplumtantite Chadwickite Chrombismite Cuprotungstite Ecdemite Grechishchevite Kamaishilite

Koninckite Lannonite Mongolite Oulankaite Pintadoite Przhevalskite Radhakrishnaite Sincosite

ditetragonal prism is often combined with the 1st order prism.Although the prism is not present and therefore is simply at the junction of the two faces, we have marked its position if it had been expressed by an arrow and the letter m. The next forms in this system to consider have the Hermann-Mauguin symmetry notation of -42m. These closed forms include the tetragonal scalenohedron (AKA rhombic scalenohedron) and the disphenoid (AKA tetragonal tetrahedron). Important to remember with both these forms is the existence of a 4-fold axis of rotary inversion. The tetragonal disphenoid exists as both a positive and negative form. It has only 4 faces. Both forms may be expressed on a single crystal. The faces are designated by the letter p for the posi9 minerals tive form and p1 for the from neg- the Disphenoidal Class: ative form. This form differs Cahnite from the tetrahedron of theNickelphosphide Crookesite Schreibersite isometric system in that the Kesterite Tillmannsite vertical axis is not the same length as the other Meliphanitetwo axes. Tugtupite The only commonNagyagite mineral in this class is chalcopyrite. Any mineral thought to be in this class must have very accurate interfacial angle measurements made to prove it is tetragonal and not isometric. The tetragonal scalenohedron (fig. 4.9) is rare by itself, but is often expressed with other forms on chalcopyrite and stannite. It may be derived from the disphenoid form of this system by drawing a line from one corner of each disphenoid face to the center of the line joining the two opposite corners, and raising two faces from the resulting division. Thus, from a 4-faced disphenoid form, we derive an 8-faced form. If you are still having trouble visualizing the form in figure 4.9, you might try thinking of it as the combination of 4 classic diamond - shaped kites, every other one in an upside down orientation! This form really was a problem for my 60 illustrator to the Dipyramidal Class: minerals from draw! An open form in this sysAmmonioleucite Jeanbandyite Mopungite Scheelite tem is the ditetragonal pyrAnkangite Julienite Narsarsukite Schwertmannite amid, whose general notation Novacekite Silvialite is {hkl}. This Arsenuranospathite form has no Kafehydrocyanite Novodneprite Stolzite symmetry plane Ashburtonite in relation Kahlerite to the 2 horizontal a axes. The Baotite Leucite Paceite Stottite symmetry notation is 4mm. Two Bariosincosite Lingunite Paraniite-(Y) Tetrarooseveltite orientations of this form in Bellidoite Manganvesuvianite Polhemusite Tetrawickmanite relation to the a axes exist, Braggite and the Manjiroite Powellite Toyohaite one noted as {hhl} Chantalite Priderite Vernadite other as {h0l}. Along with Mannardite the ditetragonal pyramid may beMarialite an Fergusonite-(Ce) Redledgeit Vesuvianite open single-faced form termed Fergusonite-(Nd) Meionite Reidite Vlodavetsite a pedion, having a Miller Fergusonite-(Y) Metalodevite Rhodostannite Vysotskite indices of {001}. The pediFormanite-(Y) Metanovacekite Rosenbergite Weddellite on will be a single face perGarronite Metatorbernite Sarcolite Wiserite pendicular to the c axis that “cuts off� the Henrymeyerite sharp terminaMetazeunerite Scapolite Wulfenite tion of the ditetragonal pyra10 mid. There are upper and lower forms for both the ditetragonal pyramid and the pedion, the upper being considered positive and the lower negative (just like the orienta

Disphenoidal

Dipyramidal

Pyramidal

5 minerals from the Pyramidal Class: Percleveite-(Ce) Pinnoite Piypite Richellite Stenhuggarite.

Ditetragonal Pyramidal

9 minerals from the Ditetragonal Pyramidal Class: Adranosite Diaboleite Diomignite Fresnoite Hematophanite Horomanite IMA2008-035 Lenaite

Nielsenite Niveolanite Routhierite Samaniite Wakefieldite-(La) Wakefieldite-(Nd) Zhangpeishanite.

11

The ditetragonal pyramid looks like one half of the ditetragonal dipyramid, but on a wellformed example is present on only one end of the c axis! This form is rarely dominant, usually being subordinant to other common prism and dipyramidal forms. Diaboleite is the only mineral known to represent this crystal class. It is interesting to note that although the mineral diaboleite was first described in 1923, it was not until 1941 that crystallographers had comprehensively investigated its forms, allowing the recognition of this form. In literature earlier than 1941, you will find the note that no mineral is known to exist in this crystal class. The tetragonal trapezohedron is the next form to consider. It is a closed form consisting of 8 trapezohedral faces, which correspond to half the faces of the ditetragonal mineralsnotafrom the Scalenohedral Class: dipyramid. Its 39 symmetry tion is 422, having Akermanite a 4-fold Jasmundite Renierite rotational axisAlumoakermanite parallel toChalcopyrite Chatkalite Kalborsite Roquesite the c axis and Archerite 2 2-fold axes Eskebornite Kuramite Santarosaite at right angles to the c axis. BariopharmacoFamatinite Laforetite Stalderite Missing are a center of symsiderite Ferrokesterite Luzonite Stannite metry and any mirror planes. Barium-zinc-alumoGallite Mawsonite Tetranatrolite There exists rightand left-handed forms (fig. 4.11). pharmacosiderite Gehlenite Melilite Urea Only phosgeniteBarquillite represents Gonnardite Mooihoekite Velikite this crystal class. Biphosphammite Gugiaite Okayamalite In a simple form drawing (desPermingeatite ignated as e inBriartite figs. 4.12aHardystonite Pirquitasite and 4.12b), theCernyite tetragonal Hocartite dipyramid appears to have a higher symmetry than 4/m, but when viewed as displayed on an actual crystal of scheelite (blue faces on fig. 4.12b), the true symmetry is revealed. Minerals possibly expressing this closed crystal form, aside from scheelite,include powellite, fergusonite, and members of the scapolite group. Our next form is an interesting one in that it possesses only a 4-fold axis of rotary inversion corresponding to the c axis. Its symmetry notation is -4. The closed form of this tetragonal disphenoid (AKA tetragonal tetrahedron) possesses only 4 faces, which are isoceles triangles (fig. 4.13). Without other modifying forms, like the pinacoid and tetragonal prisms, the form will appear to have 23 two vertical minerals from the Trapezohedral Class: symmetry planes present, giving it the symmetry of -42mMellite Cristobalite Wardite (like the disphenoid we disMillisite Zdenekite cussed above). Cyrilovite Only one minParatellurite Zinclipscombite eral - cahnite Ekanite - is known to represent this Formicaite class. Pottsite We have now reached Genkinite our final Retgersite form in the tetragonal system. Kamphaugite-(Y) Saryarkite-(Y) Although it looks simple, it, Lemanskiitehas very Sweetite like the last form, Lipscombite Ungavaite low symmetry. The tetragonal pyramid (AKA hemihedral hemiMahnertite Uytenbogaardtite morphic) is an Maucherite open form with only a 4-fold axis of rota-Vinciennite 12 tion corresponding to the c axis (fig. 4.14). The term hemimorphic sounds fancy, but is simply a short way of saying that it appears that only half a form is displayed! No

Scalenohedral

Trapezohedral

center of symmetry or mirror planes exist in this class. It has both upper {hkl} and lower {hk-l) forms, each having right- and left-hand variations. Two other tetragonal pyramids have the general form notation of {hhl} and {0kl}, depending on their form orientation to the axial cross. Wulfenite is the only mineral species to represent this form, although its crystals do not always show the difference between the pyramidal faces, above and below, to characterize distinct complimentary forms.

Ditetragonal Dipyramidal

171minerals from the Ditetragonal Dipyramidal Class: Abernathyite Abswurmbachite Aminoffite Anatase Anyuiite Apophyllite Apophyllite-(KF) Apophyllite-(KOH) Apuanite Arapovite Argutite Arsenohauchecornite Ashcroftine-(Ce) Ashcroftine-(Y) Ashoverite Asisite Atlasovite Autunite Babefphite Bambollaite Bandylite Bartonite Behierite Bismoclite Bismutohauchecornite Bortnikovite Braunite-I Braunite-II Bukovite Bystromite Calomel Cameronite Caminite Carletonite Cassiterite Cerchiaraite Chalcothallite Chernikovite Chernovite-(Ce) Chernovite-(Y) Chiolite Chlorbartonite Chromatite

Coccinite Coffinite Cooperite Cumengite Cuprorivaite Cuprostibite Daubreeite Denningite Donathite Downeyit Dreyerite Effenbergerite Ferdisilicite Ferronickelplatinum Fluorvesuvianite Fullerite Gainesit Gillespite Hauchecornite Hausmannite Henritermierite Hetaerolite Hiarneite Holtstamite Hydrohetaerolite Hydroromarchite Ilmenorutile Indium Iraqite-(La) Iwakiite Jalpaite Juanitaite Khatyrkite Kusachiite Kuzminite Leadamalgam Litharge Macedonite Mackayite Mackinawite Matlockite Mccrillisite Melanophlogite Meta-ankoleite

Meta-autunite Metakahlerite Metakirchheimerite Metauranospinite Minium Mitscherlichite Moschelite Muirite Murunskite Natisite Natrouranospinite Neltnerite Ordonezite Paramelaconite Parkinsonite Pertlikite Philolithite Phosgenite Plattnerite Potarite Pretulite Pseudoboleite Pyrolusite Quadratite Roggianite Romarchite Rorisite Rutile Sabatierite Sabugalite Saleeite Schafarzikite Schiavinatoite Schwartzembergite Selenojalpaite Sellaite Selwynite Sherwoodite Sitinakite Sodium meta-autunite Sodium-autunite Squawcreekite Steacyite

Stishovite Struverite Sugakiite Tapiolite Tapiolite-(Fe) Tapiolite-(Mn) Teepleite Tellurohauchecornite Tetra-auricupride Tetraferroplatinum Tetrataenite Thalcusite Thorikosite Thorite Thorogummite Tin Torbernite Trippkeite Tripuhyite Trogerite Tschernichite Tucekite Tulameenite Tunisite Turkestanite Uramarsite Uramphite Uranocircite Urvantsevite Varlamoffite Wakefieldite-(Ce) Wakefieldite-(Y) Wesselsite Wiluite Xenotime-(Y) Xenotime-(Yb) Zavaritskite Zeunerite Zircon

13

the axial cross for this system. emember in Article 4, the tetragtem, we held the a and b axes the gth (a1 and a2) and varied the f the c axis. Well, in the ortc system, we will continue the 90 ngular relationships between all but will vary the length of each al axis. Note that THE 3 AXES UNEQUAL IN LENGTH. If any two are hen, by convention, we are disthe tetragonal system. e 5.1, by current practice we ny crystal in this system so length of c is greater than the f a, which, in turn, is greater length of b. You will commonly s in textbooks as “c<a<b�. y also be 3 mirror symmetry which must be at right angles to er. But guess what! In the past, gists have not always observed l length practice given here, and y, the consensus is to conform sible to the existing literature. son is why we will encounter cial orientation situations when with certain common orthorhombic . mining an orthorhombic crystal, that the highest obtainable sym2-fold. In a simple form, like ination of the 3 pinacoids (open he crystal takes on an elongate, n tabular appearance. These are forms to see expressed on barite stine. nacoids are at right angles to er and usually the orientation en crystal to the axes is accomby an examination of the habit apparent cleavage. In topaz, the t pinacoidal cleavage is in the the 2 shortest axes and perpento the longest axis, so by conit is considered perpendicular axis. you will often encounter the n where a given crystal displays rominent pinacoid and the crystal ar in form. In such a case, we sider the c axis at right angle rominent pinacoid and the crysriented as in Figure 5.2. This h different appearance than the of topaz, noted in the paragraph orhombic system has 3 general classes, each expressed by its ann-Mauguin notation. ok at the forms designated by the 2/m2/m2/m. There are 3 of these u noticed that almost everything d in this article is in 3’s!): coid (also called the parallelothe rhombic prism; and the rhomramid. coid consists of 2 parallel faccan occur in the 3 different ographic orientations. These are that intercept the c axis and llel to the a and b axes {001}; that intercept the b axis and llel to the a and c axes {010}; pair that intercept the a axis parallel to the b and c axes hey are called the c pinacoid, nacoid, and the a pinacoid, rely (fig. 5.3). bic prism, an open form, consists es which are parallel to 1 axis rsect the other two. There are se rhombic prisms and they are the general notational forms: hich is parallel to the c axis; hich is parallel to the b axis; }, which is parallel to the a gure 5.4 a,b,c present the 3 prisms, each in combination with ponding pinacoidal form. Only the face of the rhombic prism is lathese examples. sm {110} and {001} 5.4b Prism {101} and {010} 5.4c Rhombic prism coid {100} we may discover after examining number of different orthorhombic that we see a large number of rms expressed on a single crysthese forms cannot be expressed ty in their numbers because their ts upon the horizontal axes are ortionate to their unit lengths. where our general symbol notation handy. In the old days of crysphy, these forms were designated r macroprisms or bracyprisms, deon whether h > k or k > h. A machas the general symbol of {h0l} acyprism has the general symbol . 14 ro- Brachy- and nacoids 5.5b Prism and Basal 5.5c ure 5.5, we have 3 sets of prisms d by the letter designations of d n, and a pinacoid face letgnated as a.

Orthorhombic

The Orthorhombic System 3 Classes: Pyramidal Disphenoidal Dipyramidal

Axial Configuration: Three axes labeled a, b and c. All axes at 90째 angles and all three of different lengths.

c -a b

-b a -c

172 minerals from unknown or uncertain class: Aldermanite Aldzhanite Almbosite Arcubisite Arsenobismite Arzrunite Athabascaite Attikaite Auroantimonate Bario-orthojoaquinite Bassanite Bertossaite Beryllite Bismutoplagionite Bogvadite Bostwickite Boulangerite Bulachite Calumetite Cebollite Chelyabinskite Chenguodaite Cheremnykhite Chessexite Chlorocalcite Chrysocolla Chubutite Cobaltzippeite Comancheite Corrensite Cowlesite Cupalite Cyanotrichite Danielsite Deliensite Dorfmanite Duhamelite Duranusite Ekmanite Erlianite Eyselite Fahleite Ferrimolybdite

Fukalite Gonyerite Gortdrumite Haynesite Heliophyllite Hydroglauberite Iddingsite Idrialite IMA2000-020 Ishikawaite Janggunite Jarosewichite Joliotite Juanite Jungite Kamarizaite Karibibite Kimuraite-(Y) Kivuite Kolarite Komarovite Kumdykolite Kuranakhite Kurumsakite Larosite Laubmannite Lavendulan Lazarenkoite Lepersonnite-(Gd) Liskeardite Loranskite-(Y) Lorettoite Loughlinite Magbasite Matveevite Mazzettiite Mengxianminite Metacalciouranoite Metasideronatrite Metauranopilite Metazellerite Moolooite Mundite

Nakauriite Natrozippeite Nepskoeite Nickelzippeite Oenite Oosterboschite Orthochamosite Orthochevkinite Orthochrysotile Orthojoaquinite-(Ce) Otwayite Oursinite Oyelite Parachrysotile Parajamesonite Pararsenolamprite Paraumbite Phyllotungstite Pingguite Piretite Plumalsite Plumbotelluritem Pseudo-autunite Rabejacite Raguinite Rhodarsenide Rickardite Sasaite Satimolite Satpaevite Scheteligite Sedovite Seifertite Sharpite Shubnikovite Silhydrite Simferite Smolianinovite Sopcheite Spadaite Stanleyite Stibioenargite Strelkinite

Swaknoite Synchysite-(Nd) Szenicsite Taimyrite Tatarskite Tatyanaite Temagamite Terlinguacreekite Theisite Tiettaite Tinnunculite Tischendorfite Tlalocite Tosudite Tsugaruite Tvedalite Urancalcarite Uranotungstite Ursilite Ustarasite Uvanite Vantasselite Vitusite-(Ce) Vyacheslavite Walentaite Watanabeite Wattevilleite Widenmannite Wolsendorfite Xocomecatlite Yaroslavite Yttrocolumbite-(Y) Yttrocrasite-(Y) Zellerite Zinc-zippeite Zinclavendulan Zincosite Zoubekite Zykaite

15

of which intersects all 3 crystallographic axes. This pyramid may have several different appearances due to the variability of the axial lengths (figs. 5.6 a,b,c). 5.6a Rhombic dipyramid 5.6b 5.6c Sulfur crystal A relatively large number of orthorhombic minerals are encountered with combinations of the various forms presented so far. These include andalusite, the members of the aragonite and barite group, brookite, chrysoberyl, the orthopyroxenes, goethite, marcasite, olivine, sillimanite, stibnite, sulfur, and topaz. Next to consider are the few forms having the symmetry mm2 (termed the rhombic pyramidal). The two-fold rotational axis corresponds to the c crystallographic axis and the 2 mirror planes (at right angles to each other) intersect this axis. Due to the fact that no horizontal mirror plane exists, forms at the top and bottom of the crystal are different. Look at Figure 5.7a. Also, due to the lack of the horizontal mirror plane, there exists no prisms, but instead we have 2 domes in place of each of the prisms (do you remember that a dome consists of 2 faces that intersect each other, but have no corresponding parallel faces on the other end of the crystal?). Think of the minerals hemimorphite (fig. 5.7b), struvite (fig. 5.7c) or bertrandite when you think of this symmetry class. 5.7a Rhombic pyramid 5.7b Hemimorphite 5.7c Struvite And now to the last (and the lowest) symmetry class of the orthorhombic system, the rhombic disphenoid. from the Pyramidal Class: The Elpidite form has also been called the rhombic Bismutite Chambersite tetrahedron. It has the symmetry notation of 222,Emilite that is 3 axes of 2-fold rotation which Blossite Chesterite correspond with the 3 crystallographic axes. Boracite Childrenite Enargite I’m Ericaite sorry, but there is just no other symmeBorishanskiite Chkalovite try here! The forms are, however, enantioBoromullite Cobaltite Flagstaffite morphic, that is to say present as right and Bredigite Costibite leftFourmarierite images (fig. 5.8). These closed forms consist of 2 upper triangular faces which Buchwaldite CaleDamaraite Friedrichite alternate with 2 lower triangular faces, donite Daomanite the Gabrielsonite pair of upper faces being offset by 90 degrees in relation to the pair of lower Canfieldite Derriksite Gaidonnayite faces. Carbocernaite Dittmarite Gaultite

Pyramidal

133 minerals Alfredstelznerite Althausite Argyrodite Armenite Banalsite Barioperovskite Barylite Batisite Bavenite Becquerelite Bertrandite Billietite

Caysichite-(Y) Cervantite

Dyscrasite Edenharterite

Gobbinsite +

Disphenoidal

88 minerals from the Disphenoidal Class:

16

Adelite Aguilarite Alloclasite Arsendescloizite Arsenoclasite Austinite Balkanite Behoite Billingsleyite Byelorussite-(Ce) Calkinsite-(Ce) Capgaronnite

Chalcomenite Cobaltaustinite Conichalcite Dilithium Dinite Duftite-alpha Duftite-beta Edingtonite Epsomite Euchroite Foggite Gatehouseite

Gerhardtite Godlevskite Goslarite Gottlobite Haineaultite Haycockite Hydroxylbastnasite Jeffreyite Karlite Kurchatovite Lapieite Lautite

Lecontite Lenoblite Lisiguangite Lisitsynite Lueshite Melanotekite Mendipite Morenosite

Mozartite Muckeite Nabesite +

Dipyramidal

577 minerals from the Disphenoidal Class: Adamite Aeschynite-(Ce) Aeschynite-(Nd) Aeschynite-(Y) Agrinierite Aikinite Pbnm Aksaite Allabogdanite Alumotantite Ancylite-(Ce) Ancylite-(La) Andalusite Andorite Andreyivanovite Anduoite Anglesite Anhydrite Anilite Anthophyllite Antimonselite Antlerite Apophyllite-(NaF) Aragonite Arcanite Ardennite-(As) Ardennite-(V) Argentopyrite Armalcolite Arsenolamprite Arsenuranylite Ashanite Atacamite Avogadrite Azoproite Balipholite Balyakinite Barberiite Barite Barrerite Bederite Benyacarite Bernalite Berthierite Betekhtinite Beyerite Bezsmertnovite Bigcreekite Birchite Bismuthinite Bismutocolumbite

Bismutotantalite Blatterite Boehmite Boggsite Bonaccordite Bornite Bournonite Bowieite Bracewellite Brassite Brenkite Brookite Brownmillerite Buckhornite Burkeite Bursaite Cabriite Calciborite Calcioancylite-(Ce) Calcioandyrobertsite Calciocatapleiite Calzirtite Carminite Carnallite Carpholite Cassagnaite Catalanoite Cavansite Cavoite Cechite Celestine Cerussite Cesbronite Cesbronite-x Chalcocyanite Chalcostibite Chegemite Chelkarite Cherepanovite Chesnokovite Chestermanite Chiavennite Chlorothioite Chrysoberyl Clerite Clinobarylite Cohenite Colimaite Columbite-(Fe) Columbite-(Mg)

Columbite-(Mn) Compreignacite Coparsite Cordierite Cornetite Cosalite Cotunnite Coutinhoite Creaseyite Cubanite Curienite Curite Cyanophyllite Danburite Dawsonite Defernite Delhayelite Demicheleite-(Br) Descloizite Diaspore Dimorphite Direnzoite Donpeacorite Dovyrenite Dresserite Dumortierite Dundasite Eclarite Emeleusite Emplectite Empressite Enstatite Eosphorite Epididymite Ercitite Eriochalcite Erythrosiderite Eucairite Euxenite-(Y) Evenkite Falcondoite Fangite Fayalite Fedorovskite Ferrierite-K Ferrierite-Mg Ferrisicklerite Ferro-anthophyllite Ferrocarpholite Ferrogedrite

Ferroholmquistite Ferronordite-(Ce) Ferronordite-(La) Ferroselite Ferrosilite Ferruccite Fersmite Filipstadite Flinkite Florenskyite Fluellite Forsterite Francevillite Francisite Fredrikssonite Fritzscheite Frohbergite Frondelite Galenobismutite Garavellite Garyansellite Gedrite Gerstmannite Gladite Glaucochroite Glaucodot Goethite Gottardiite Graemite Grandidierite Gravegliaite Grischunite Groutite Guanajuatite Gustavite Guyanaite Gwihabaite Gysinite-(Nd) Haidingerite Haiweeite Hambergite Hammarite Hanawaltite Hannebachite Hashemite Hastite Hazenite Heklaite Hendersonite +

17

Hexagonal

18

The Hexagonal System 7 Classes: Trigonal Dipyramidal Dipyramidal Trapezohedral Ditrigonal Dipyramidal Pyramidal Dihexagonal Pyramidal Dihexagonal Dipyramidal Axial Configuration: Four axes. Three of the axes fall in the same plane and intersect at the axial cross at 120째. These three axes labeled a1, a2and a3 are the same length. The fourth axis, labeled c, may be longer or shorter than the a axes set. The c axis also passes through the intersection of the a axes set at 90째 to the plane formed by the a set.

c -a1 a2 -a3

a3

-a2 a1

-c

52 minerals from unknown or uncertain class: Afghanite Arnhemite Asbolane Bayankhanite Bellbergite Blatonite Braitschite-(Ce) Carraraite Carrboydite Chiluite Chlormagaluminite Cuzticite Feitknechtite Felsobanyaite

Feroxyhyte Fluocerite-(La) Goudeyite Guarinoite Hydrohonessite Hypercinnabar Jamborite Johnbaumite Karnasurtite-(Ce) Lourenswalsite Majakite Menshikovite Mertieite-I Minehillite

Mongshanite Morelandite Mountkeithite Nagelschmidtite Namuwite Oregonite Orickite Pimelite Plumbonacrite Rancieite Saddlebackite Schulenbergite Takanelite Tocornalite

Tranquillityite Ungursaite Vozhminite Wallkilldellite-(Fe) Wardsmithite Woodwardite Zemkorite Zincaluminite Zn-Schulenbergite

19

Trigonal Dipyramidal

3 minerals from the Trigonal Dipyramidal Class: Cesanite Laurelite Reederite-(Y)

Dipyramidal

62 minerals from the Dipyramidal Class:

20

Agardite-(Ca) Agardite-(Ce) Agardite-(Dy) Agardite-(La) Agardite-(Nd) Agardite-(Y) Aiolosite Alforsite Apatite Apatite-(CaCl) Apatite-(CaF) Apatite-(CaOH) Apatite-(SrOH) Britholite-(Ce) Britholite-(Y) Calciopetersite Davyne Ellestadite

Ellestadite-(Cl) Ellestadite-(F) Ellestadite-(OH) Fermorite Fluoborite Fluorbritholite-(Ce) Fluorcalciobritholite Hanksite Hedyphane Hydroxylborite Hydroxylpyromorphite IMA2008-068 IMA2009-015 Inaglyite Irtyshite Jeremejevite Jouravskite

Keystoneite Kinichilite Konderite Mattheddleite Mimetite Mineevite-(Y) Mixite Nasonite Painite Petersite-(Y) Phosphohedyphane Plumboagardite Polkanovite Pyromorphite Quadridavyne Svabite Thaumasite Tienshanite

Tritomite-(Ce) Tritomite-(Y) Turneaureite Vanadinite Wadeite Zalesiite Zemannite

Trapezohedral

26 minerals from the Trapezohedral Class: Brockite Calciotantite Charmarite-2H Edgarite Faheyite Grayite Iltisite Kaliophilite Kraisslite Mallestigite

Microsommite Molybdophyllite Palarstanide Parakhinite Penzhinite Quetzalcoatlite Quintinite-2H Rhabdophane-(Ce) Rhabdophane-(La) Rhabdophane-(Nd)

Santanaite Siderazot Tounkite Tristramite Virgilite Vishnevite

Ditrigonal Dipyramidal

25 minerals from the Ditrigonal Dipyramidal Class: Barringerite Bastnasite-(Ce) Bastnasite-(La) Bastnasite-(Y) Bazirite Belkovite Benitoite Connellite Despujolsite Grimselite

Hydroxylbastnasite IMA2009-013 Jagoite Liottite Monipite Offretite Pabstite Peprossiite-(Ce) Pittongit Qusongite

Schaurteite Thorbastnasite Traskite Wenkite

21

ion. he forms of the hexagonal system are defined by he axial cross relationships. The hexagonal axes fig. 6.1) consist of 4 axes, 3 of which are of qual length and in the same plane, as proposed by ravais. These 3 axes, labeled a1, a2, and a3 have n angular relationship to each other of 120 derees (between the + ends). At right angle (geometical mathematicians say “normal”) to the plane of he a axes is the c axis. Its length may vary from ess than to greater than the length of any of the axes. It will not equal the length of an a axis, owever. ote the orientation of the 4 axes and their + and ends. If viewed vertically (down the c axis), he axes divide a circle into 6 equal parts and he axial notation reads (starting with a +) as ,-,+,-,+,-. The positive and negative ends alterating. In stating the indices of any face, four umbers (the Bravais symbol) must be given. In the ermann-Mauguin symmetry notation, the first numer refers to the principal axis of symmetry, which

Pyramidal

has two divisions, based on symmetry. There are seven possible classes, all having 6-fold symmetry, in the Hexagonal division and five possible classes, all having 3-fold symmetry, in the Trigonal division. The general symbol for any form in the Hexagonal system is {hk-il}. The angular relation of the three horizontal axes (a1, a2, a3) shows that the algebraic sum of the indices h, k, i, is equal to 0. The Hexagonal Division Now, let’s begin to consider the first class of the Hexagonal division. The Normal or Dihexagonal dipyramidalclass has 6-fold symmetry around the c or vertical axis. It also has 6 horizontal axes of 2-fold symmetry, 3 of which correspond to the 3 horizontal crystallographic axes and 3 which bisect the angles between the axes. It’s Hermann- Mauguin notation is 6/m2/m2/m. Confused? Check out figure 6.2a and 6.2b which show the symmetry elements of this class, associated with axes and mirror planes. 6.2a & 6.2b symmetry elements

28 minerals from the Pyramidal Class: Berborite Cancrinite Cancrisilite Cetineite Ekaterinite Ellenbergerite Finnemanite Fluorcaphite Gaudefroyite Gyrolite

Hydroxycancrinite IMA2008-065 IMA2008-069 Kambaldaite Kellyite Kyanoxalite Malinkoite Megakalsilite Micheelsenite Nepheline

Ottensite Panunzite Pitiglianoite Szymanskiite Theresemagnanite Tiptopite Trikalsilite Zinkenite

Dihexagonal Pyramidal

ee figure 6.10 for a beryl rystal having all these forms isplayed. Molybdenite and pyrhotite also crystallize in this lass. he ditrigonal dipyramid{hk-il} as a 6-fold rotoinversion axis, hich is chosen as c. We should ote that -6 is equivalent to 3-fold axis of rotation with mirror plane normal to it. hree mirror planes intersect he vertical axis and are perendicular to the 3 horizontal rystallographic axes. There are lso 3 horizontal 2-fold axes of ymmetry in the vertical mirror lanes. The Herman-Mauguin nota34 minerals ion is -6m2. Akdalaite his class is a 12-faced form ith six faces aboveBrokenhillite and 6 facs below the mirror Bromellite plane that ies in the a1-a2-a3 axial plane. igure 6.11a is the Cadmoselite ditrigonal ipyramid form and figure 6.11b isplays a drawing of benitoite, Calcioburbankite he only mineral described in Demartinite his class. Ekatite he Hemimorphic (dihexagonal pyrmid) class. This class differs Ewaldite rom the above discussed classs in that it has noFerrohogbomite horizontal lane of symmetry and no horizonGengenbachite al axes of symmetry. There is no enter of symmetry. Therefore, 22 he Hermann-Mauguin notation is mm. The geometry of the prisms s the same. The basal plane is a edion (remember a pedion differs rom a pinacoid in that it is a ingle face) and the positive and egative pyramids of the 3 types. he difference may be readily

6.13a, b, & c).

rotation and a symmetry plane normal to it (3/m). See figure 6.16. In the Hexagonal Trapezohedral class, the symmetry axes are the Mathematically, this class may same as the Normal (dihexagoexist, but to date no mineral is nal dipyramidal class discussed known to crystallize with this initially in this section), but form. mirror planes and the center of In the Hexagonal pyramid class, symmetry are not present. The the vertical axis is one of Hermann-Mauguin notation is 622. 6-fold rotation. No other symTwo enantiomorphic (mirror image) metry is present. Figure 6.17 forms are present, each having 12 is the hexagonal pyramid. The trapezium-shaped faces (figure forms of this class are simi6.14). lar to those of the Hexagonal Dipyramid (discussed above), but Other forms, including pinacoid, because there is no horizontal hexagonal prisms, dipyramids, and mirror plane, different forms from the Dihexagonal PyramidalClass: dihexagonal prisms, may be presare present at the top and botent. Greenockite Only 2 minerals are known tom of the crystal. The hexagonal Yarlongite to represent this crystalMoissanite class: pyramid has four 6-faced forms: high Gregoryite (beta) quartz and kalsilite. upper positive, upper negative, Nolanite Zincite lower positive, lower negative. IMA2003-019 Dipyramid class Orcelite The Hexagonal Pedions, Zincohogbomite hexagonal pyramids and (figure 6.15) has only the vertiprisms may be present. Only rareIodargyrite Phosphoellenbergerite cal 6-fold axis of rotation and a ly is the form development suffisymmetry plane perpendicular to cient to place a crystal in this Jedwabite Rambergite it. The Hermann-Mauguin notation class. Nepheline is the most comKamiokite is 6/m. When this form isRinmanite by itmon representative of this class. self,Khanneshite it appears to possess highThe Trigonal Division Sanromanite er symmetry. However, in combination Kleberite with other forms it Stibiopalladinite reveals Now we have worked through the its low symmetry content. first 7 classes in the Hexagonal Magnesiohogbomite Swedenborgite System, all having some degree The general forms of thisWurtzite class of 6-fold symmetry. Time to shed Magnesiotaaffeite are positive and negative hexagothat 6-fold symmetry and look at nal dipyramids. These forms have the Trigonal Division of the Hex12 faces, 6 above and 6 below, agonal System. Here, we will see and correspond in position to that 3-fold symmetry rules. one-half of the faces of a dihexagonal dipyramid. Remember that prisms are open forms. In the trigonal division Other forms present may include there are two distinctive sets pinacoid and prisms. The chief of prisms to be concerned with. minerals crystallizing in this The first is called the trigonal

1. Base or basal pinacoid 2 (0001) open 2. First order prism 6 (10-10) open 3. Second order prism 6 (11-20) open 4. Dihexagonal prism 12 (hk-i0) example: (2130) open 5. First order pyramid 12 (h0-hl) example: (1011), (20-21) closed 6. Second order pyramid 12 (hh2hl) example: (11-22) closed 7. Dihexagonal dipyramid 24 (hk-il) example: (21-31) closed See figures 6.3 through 6.8 (below) for what these forms look like. First order hexagonal prism and c pinacoid Second order hexagonal prism and c pinacoid Dihexagonal prism and c pinacoid First order hexagonal dipyramid Second order hexagonal dipyramid Dihexagonal dipyramid The two faces of the Base, or basal pinacoid, are normal to the c axis and parallel to each other, and are generally denoted by the italic letter c.

figure 6.9, the relationships of the two forms to each other and to the a axes are readily noted. The dihexagonal prism is a 12-sided prism bounded by 12 faces, each parallel to the vertical (c) axis. If you had both first and second order prism equally expressed on the same crystal, you could not easily tell them apart from the dihexagonal form. See figure 6.5. Corresponding to the 3 types of prisms are 3 types of pyramids. Note in the figures 6.6 and 6.7 on th previous page the similar shape, but difference in angular relation to the horizontal axes. The dihex agonal dipyramid is a double 12-sided pyramid (fig ure 6.8 ). The first order pyramid is labeled p. The second order pyramid is labeled s. The dihexag onal dipyramid is labeled v. These forms look relatively simple until several o them are combined on a single crystal, then look out! You can even have several of the same form at different angles, thus 2 first order pyramids may be labeled p and u, respectively.

Dihexagonal Dipyramidal

135 minerals from the Dihexagonal Dipyramidal Class: Achavalite Friedrichbeckeite Nezilovite Akhtenskite Gmelinite-Ca Nickeline Algodonite Gmelinite-K Niggliite Allargentum Gmelinite-Na Oftedalite Almarudite Graphite Osmium Astrocyanite-(Ce) Haggertyite Osumilite-(Fe) Atheneite Hauckite Osumilite-(Mg) Barbertonite Hawthorneite Perhamite Batiferrite Heterogenite-2H Perlialite Bazzite Hexaferrum Plumboferrite Bentorite Hexamolybdenum Plumbopalladinite Berezanskite Hexatestibiopanickelite Poudretteite Beryl Hibonite Rhenium Brannockite Ice Roedderite Breithauptite Idaite Rutheniridosmine Brugnatellite IMA2008-009 Ruthenium Burbankite IMA2008-055 Sacrofanite Burnsite IMA2009-005 Schachnerite Buttgenbachite Imgreite Sederholmite Cacoxenite Indialite Shibkovite Cadmium Jaipurite Sjogrenite Catamarcaite Kittatinnyite Sobolevskite are two principal forms in this Chaoite Kleinite In fact, the normal light-reclass: the rhombohedron Sogdianite and the fracting 60 degree glass prism hexagonal scalenohedron.Sorosite Chayesite Klochite used in many physics lab workshops is this form, bounded Claringbullite on In this Klockmannite class, the 3-fold rotoinStannopalladinite the end by the c pinacoid. There version axis is the vertical axis Cordylite-(Ce) (c) and Kokchetavite exists a second order prism, the three 2-foldStoppaniite rotation which on general appearance Covellite looks axes correspond to the three horStumpflite the same as the first order, but izontal Kotulskite axes (a1, a2, a3). when other trigonal forms are Darapiosite Koutekite Stutzite present on the termination othThere are 3 mirror planes biSudburyite er than the c pinacoid, the Diaoyudaoite two secting Langisite the angles between the prisms may be readily distinhorizontal axes. See figure 6.18 Dmisteinbergite Lindqvistite Sugilite guished, one from the other. The to observe the axes and mirror second order prism is rotated 60 planes for the rhombohedron. Drysdallite Lonsdaleite Titanium degrees about the c axis when The general form {hk-il} is a Dugganite Luanheite Trattnerite compared with the first order hexagonal scalenohedron(figure prism. 6.19). The primary difference in Dusmatovite Lukechangite-(Ce) Troilite The second prism is the ditrigothe rhombohedron and this form is nal prism, which is a 6-sided that with a rhombohedralTungstenite form, Eifelite Magnetoplumbite open form. This form consists of you have 3 rhombohedral faces Erionite-Ca Manasseite 6 vertical faces arranged in sets above and 3 rhombohedralVaterite faces of 2 faces. below the center of the Vavrinite crystal. Erionite-K Mavlyanovite Therefore the alternating edges In a scalenohedron, each of the Mazzite-Mg Verplanckite are of differing character; Erionite-Na esperhombohedral faces becomes 2 scaEttringite Mazzite-Na by dividing Wallkilldellite cially noticable when viewed by lene triangles the looking down the c axis. from upper Weishanite to lower Fairchildite rhombohedron corners Merrihueite with a line. Therefore, The differing angles between the you haveMethane 6 faces on top Weissite and 6 Farneseite hydrate-H 3 sets of faces are what distfaces below, the scalenohedron Fleischerite being a Milarite Xifengite ingish this form from the first 12-faced form. These order hexagonal prism. forms are illustrated in figure Fluocerite-(Ce)6.20. Molybdenite Yagiite The striations on the figure to With this form, you can Yimengite have both Freboldite Natrofairchildite the left are typical for natural positive {h0-hl} and negative

trigonal crystals, like tourmaline. In the drawing, c is the pinacoid face and m the prism faces. I think these forms are simple enough that we don’t need any drawings to explain them, but look for them on figure 6.23 (be-

{0h-hl} forms for the rhombohedron... and positive {hk-il} and negative {kh-il} forms for the scalenohedron. To further complicate matters, the rhombohedron and scalenohedron, as forms, often combine

Yuanjiangite Zaccagnaite Zenzenite Zinc

crystallized, and collectible mineral with these forms. See figure 6.21 for some crystallization forms of calcite. Several other minerals, such as chabazit and corundum, commonly show form combinations. On the last 3 drawings in figure 6.21, see if YOU can name th faces present. I have already given the notation in the first 5 figures. Email me with your answer, and I’ll tell you if you are right! The next crystal class to consider is the Ditrigonal pyramid. The vertical axis is a 3-fold rotation axis and 3 mirror plane intersect in this axis. The Hermann-Mauguin notation is 3m, 3 referring to the vertical axis and m referring to three planes normal to the three horizontal axes (a1,a2,a3). These 3 mirror planes intersect in the vertical 3-fold axis. The general form {hk-il} is a ditrigonal pyramidform. There ar 4 possible ditrigonal pyramids, with the indices {hk-il}, {khil}, {hk-i-l}, and {kh-i-l}. The forms are similar to the hex agonal-scalenohedral form dis23contain cussed previously, but only half the number of faces owing to the missing 2-fold rotation axes. So crystals in this class have different forms on th top of the crystal than on the bottom. Figure 6.22 shows the ditrigonal pyramid.

Trigonal

24

The Trigonal System 5 Classes: Pyramidal Ditrigonal Pyramidal Rhombohedral Trapezohedral Hexagonal Scalenohedral

Axial Configuration: Four axes. Three of the axes fall in the same plane and intersect at the axial cross at 120°. These three axes labeled a1, a2and a3 are the same length. The fourth axis, labeled c, may be longer or shorter than the a axes set. The c axis also passes through the intersection of the a axes set at 90° to the plane formed by the a set.

coid face and m the prism faces. I think these forms are simple enough that we don’t need any drawings to explain them, but look for them on figure 6.23 (below) - the tourmaline forms. They are given the normal prism notatio of m and a. Hexagonal-scalenohedral class. The firs to consider are those forms with the symmetry - 3 2/m (Hermann-Mauguin notation). There are two principal forms in this class: the rhombohedron and the hexagonal scalenohedron. In this class, the 3-fold rotoinversion axis is the vertical axis (c) and the three 2-fold rotation axes correspond t the three horizontal axes (a1, a2, a3). There are 3 mirror planes bisecting the angles between the horizontal axes. See figure 6.18 to observe the axes and mir ror planes for the rhombohedron. The general form {hk-il} is a hexagonal scalenohedron(figure 6.19). The primary difference in the rhombohedron and this form is that with a rhombohedral form, you have 3 rhombohedral faces above and 3 rhombohedral faces below the center o the crystal. In a scalenohedron, each of the rhombohedral faces becomes 2 scalene triangle by dividing the rhombohedron from upper to lower corners with a line. Therefore you have 6 faces on top and 6 faces below, the scalenohedron being a 12-faced form. These forms are illustrated in figure 6.20. With this form, you can have both positive {h0-hl} and negative {0h-hl} forms for the rhombohedron... and positive {hk-il} and negative {khil} forms for the scalenohedron. To further complicate matters, the rhom bohedron and scalenohedron, as forms, often combine with forms present in higher hexagonal symmetry classes. Thus you may find them in combination with hexagonal prisms, hexagonal dipyramid, and pinacoid forms. Calcite is the most common, well crystallized, and collectible mineral with these forms. See figure 6.21 for some crystallization forms of calcite. Several other minerals, such as chabazite and corundum, commonly show form combinations. On the last 3 drawings in figure 6.21, see if YOU can name the faces present. I have already given the notation in the first 5 figures. Email me with your answer, and I’ll tell you if you are right! The next crystal class to consider is the Ditrigonal pyramid. The vertical axis is a 3-fold rotation axis and 3 mirror planes intersect in this axis. The Hermann-Mauguin notation is 3m, 3 referring to the vertical axis and m referring to three planes normal to the three horizontal axes (a1,a2,a3). These 3 mirror planes intersect in the vertical 3-fold axis. The general form {hk-il} is a ditrigona pyramidform. There are 4 possible ditrigonal pyramids, with the indices {hkil}, {kh-il}, {hk-i-l}, and {kh-i-l}. The forms are similar to the hexagonal-scalenohedral form discussed previously, but contain only half the number of faces owing to the missing 2-fold

c

-a1 a2 -a3

a3

-a2 a1

-c

30 Minerals from unknown or uncertain class: Alunite Babkinite Cesarolite Coombsite Cronusite Daqingshanite-(Ce) Desautelsite Droninoite Ernienickelite Francoanellite

Geerite Glaucocerinite Jianshuiite Karchevskyite Magnesionigerite Marinellite Mathewrogersite Melanocerite-(Ce) Muskoxite Nanlingite

Orlymanite Philipsbornite Romanite Stepanovite Sztrokayite Tegengrenite Truscottite Vanoxite Zhemchuzhnikovite Zirklerite

25

Pyramidal

40 minerals from the Pyramidal Class: Aktashite Averievite Bechererite Belovite-(Ce) Benstonite Biachellaite Bottinoite Brandholzite Cappelenite-(Y) Carlinite

Deloneite-(Ce) Diversilite-(Ce) Dixenite Franciscanite-III Franciscanite-VIII Ganomalite Gordaite Gruzdevite Hematolite Holfertite

Ilimaussite-(Ce) IMA2009-001 Jarosite Kelyanite Kuzelite Nowackiite Oneillite Orebroite-III Orebroite-VIII Parisite-(Ce)

rotation axes. So crystals in this clas the crystal than on the bottom. Figure Figure 6.23 shows 2 tourmaline crystals ing in this class, which display 3m sym This form may be combined with pedions, trigonal pyramids, trigonal prisms, and plicated, though interesting, forms. We now have come to the Trigonal-trapez are occupied by the rotation axes. The rotation and the 3 horizontal axes have This is similar to those in class -32/m planes of symmetry are missing. There a composed of 6 trapezium-shaped faces. T {i-k-hl}, {kh-il}, and {-ki-hl}. These phic pairs, each with a right and left 6.24). Other forms which may be present includ nal prism, ditrigonal prisms, and rhomb Quartz is the common mineral which crys rarely is the trapezohedral face (s) di matter to determine if the crystal is r 6.25). Cinnabar also crystallizes in this clas The Rhombohedral class has a 3-fold axi lent to a 3-fold axis of rotation and a is {hk-il} and the Hermann- Mauguin not This form is tricky because unless othe try will not be apparent. The pinacoid be present. Dolomite and ilmenite are the two most class. See figure 6.26.

Parisite-(Nd) Rontgenite-(Ce) Now we arrive at the final class in the amid has one 3-fold axis of rotation as Sheldrickite figure 6.27. There are, however, 8 trig Simpsonite {hk-il}, four above and four below. Eac the dihexagonal dipyramid (discussed ab Stavelotite-(La) sible that there may be trigonal pyrami dent, pyramids below. Only when several Stillwellite-(Ce) with one another is the true symmetry r Voronkovite It appears that only one mineral, a rar Welinite-III to this class and it has not been studi in some crystallographer’s minds. Welinite-VIII All crystals in the Hexagonal system ar Zussmanite

of the a3 axis (see again figure 6.1) i plotting purposes. This becomes importa of rhombohedral forms and determining i

Ditrigonal Pyramidal

112 minerals from the Ditrigonal Pyramidal Class:

26

Acetamide Aerinite Alloriite Aluminocerite-(Ce) Ammoniojarosite Aqualite Argentojarosite Arsenocrandallite Arsenoflorencite-(La)

Arsenoflorencite-(Nd) Asbecasite Beaverite Belendorffite Bobdownsite Buergerite Buryatite Bystrite Carbokentbrooksite

Cerite-(Ce) Cerite-(La) Changbaiite Charlesite Chlorartinite Chromdravite Chvilevaite Congolite Corkite Cronstedtite

Dravite Dualite Dukeite Dussertite Elbaite Ellisite Feklichevite Fencooperite Ferrokentbrooksite +

ss have different forms on the top of 6.22 shows the ditrigonal pyramid. s, the most common mineral crystallizmmetry. , hexagonal prisms and pyramids, d ditrigonal prisms to yield some comzohedral class. The 4 axial directions vertical axis is an axis of 3-fold e 2-fold symmetry. m (hexagonal-scalenohedron), but the are 4 trigonal trapezohedrons, each Their Miller indices are: {hk-il}, forms correspond to 2 enantiomorform (one pair illustrated in figure de pinacoid, trigonal prisms, hexagobohedrons. stallizes in this class, but only isplayed. When it is, it is a simple right- or left-handed in form (figure

Rhombohedral

ss. is of rotoinversion, which is equivaa center of symmetry. The general form tation is -3. er forms are present, its true symme{0001} and the hexagonal prisms may

79inminerals common minerals crystallizing this

Akimotoite Allendeite e Hexagonal system. The Trigonal pyrAndersonite s its sole element of symmetry. See gonal pyramids of the generalAnkerite form ch of these correspond to 3 faces of Armangite bove). In addition to this, it is posids above and equivalent, butBelovite-(La) indepenl trigonal pyramids are in combination Brizziite-III revealed. Brizziite-VII re species called gratonite, Burtite belongs ied sufficiently to remove all doubt Chalcophanite Chladniite re oriented so that the negative end Cleusonite

is considered to be 0 degrees for ant when looking at the distribution if they are + or -.

from the Rhombohedral Class: Crichtonite Cualstibite Davidite-(Ce) Davidite-(La) Dessauite Dioptase Dolomite Ecandrewsite Eitelite Erniggliite Eucryptite Ferrinatrite

Fibroferrite Fillowite Gagarinite-(Y) Galileiite Geikielite Gillardite Gramaccioliite-(Y) Haydeeite Humberstonite Hyttsjoite Ilmenite IMA2008-006

Jaffeite Johnsomervilleite Keithconnite Kuannersuite-(Ce) Kutnohorite Landauite Lindsleyite Loveringite Loweite Mathiasite Melanostibite +

Trapezohedral

36 minerals from the Trapezohedral Class: Abhurite Alarsite Antarcticite Berlinite Calciohilairite Caresite Charmarite Cinnabar Combeite Franzinite

Godovikovite Heazlewoodite Huntite Ingersonite Joelbruggerite Komkovite Malladrite Manganarsite Monohydrocalcite Norsethite

Olekminskite Paralstonite Pseudorutile Pyatenkoite-(Y) Quartz Quintinite-3T Rodolicoite Sabieite Sazykinaite-(Y) Schuetteite

Selenium Sergeevite Tellurium Tincalconite Ximengite Zirconolite-3T

27

Hexagonal Scalenohedral

208 minerals from the Hexagonal Scalenohedral Class:

28

Abenakiite-(Ce) Aerugite Aleksite Alluaivite Amakinite Ammonioalunite Antimony Aphthitalite Arctite Arsenic Arsenoflorencite-(Ce) Arsenogorceixite Arsenogoyazite Arsenowaylandite Baksanite Bararite Bario-olgite Barysilite Benauite Berndtite Beudantite Bismuth Bobtraillite Bohdanowiczite Brucite Butschliite Calcite Carlosruizite Caswellsilverite Chabazite-K Chabazite-Na Chabazite-Sr Chalcophyllite Chloraluminite Chlormanganokalite Chloromagnesite Clarkeite Coalingite Colquiriite Comblainite Coquimbite Corundum Crandallite Cupropearceite

Cupropolybasite Delafossite Digenite Dorallcharite Eirikite Eskolaite Eudialyte Eylettersite Ferrihydrite Ferrotaaffeite Florencite-(Ce) Florencite-(La) Florencite-(Nd) Fougerite Fuenzalidaite Gaspeite Gorceixite Goyazite Graulichite-(Ce) Grimaldiite Haapalaite Harkerite Harrisonite Hedleyite Hematite Herbertsmithite Herschelite Heterogenite Hidalgoite Hilairite Hinsdalite Honessite Hongshiite Huanghoite-(Ce) Huangite Hydrotalcite Hydrowoodwardite Ikunolite Ingodite Iowaite Joseite Kalistrontite Kapellasite Karelianite

Kawazulite Kazakovite Kemmlitzite Kintoreite Kitkaite Kochkarite Koenenite Kosnarite Laitakarite Lawrencite Leifite Leisingite Levyne-Ca Levyne-Na Liandratite Lithiophorite Lovozerite Machatschkiite Magnesiohogbomite Magnesite Martyite Matildite Mcallisterite Mcconnellite Mcgovernite Meixnerite Melonite Mercury Millerite Minamiite Moncheite Motukoreaite Natroalunite Natrotantite Nelenite Nevskite Nitratine Nukundamite Olgite Orpheite Orschallite Otavite Palmierite Parabariomicrolite

Paraguanajuatite Parascorodite Pearceite Petscheckite Pilsenite Platynite Plumbogummite Plumbojarosite Portlandite Poubaite Protojoseite Proustite Pyroaurite Pyrochroite Pyrosmalite-(Fe) Pyrosmalite-(Mn) Qaqarssukite-(Ce) Reevesite Rhodochrosite Rhodplumsite Rinneite Rosiaite Rucklidgeite Scacchite Schlossmacherite Segnitite Shandite Shuangfengite Siderite Simonkolleite Skippenite Smithsonite Smythite Sphaerocobaltite Springcreekite Steenstrupine-(Ce) Stibarsen Stichtite Stistaite Sudovikovite Sulphotsumoite Svanbergite Takedaite +

29

Monoclinic

aving dispensed with the exagonal system in article , we are ready to resume ur task of the removal of ymmetry from 3-axis sysems. Consider the axial ross, consisting of the a, , and c axes (each of unqual length), of the Monolinic System (fig. 7.1). In ll previous 3-axes systems, e considered what happens hen we vary one or more of he axial lengths, retainng the axial angles at 90 egrees to each other. But n the Monoclinic System, e will look 30 at what hapens when we have 3 axes f unequal length and vary he angle off of 90 degrees etween two of the axes. Obiously, we must again lose ome symmetry! he axes are designated as

the vertical axis is c, and the remaining axis which is at right angle to the plane of the a and c axes is b. When properly oriented, the inclined axis a slopes toward the observer, b is horizontal and c is vertical. Both b and c axes are in the plane of the paper. In Figure 7.1, the angle between c and b remains 90 degrees and the angle (^) between c and a is the one we will vary. Its called beta and is represented by the Greek letter in the axial figure. For most monoclinic crystals, the ^ beta is greater than 90 degrees, but in some rare instances, the angle may be 90 degrees. When this occurs, the monoclinic symmetry is not

perpendicular to the mirror plane) is usually taken as the b axis. Then the a axis is inclined downward toward the front in the figure. Calculations of axial ratios in orthogonal crystal systems (where all the axes are perpendicular to each other) are relatively easy, but become quite tedious in systems with one or more inclined axes. I suggest an advanced mineralogy text, not an introductory one, if you ever get involved in something like this. Not even your standard mineralogy texts these days give the formulae to do these calculations. Aside from the axial constants necessary to describe minerals in the monoclinic system, the ^ beta must

for orthoclase mineralogy text Klein and Hurlb of Mineralogy a Dana. You will orthoclase a:b: 0.559. ^beta = 50 minutes. Cleavage is imp consider in thi there is a good cleavage parall b axis (as in t al orthoclase), usually called cleavage. In th pyroxenes and a where there are cleavage direct are usually con vertical prisma ages. There are only classes to cons

in a standard tbook, like butís Manual after E. S. find that for :c = 0.663:1: 115 degrees,

portant to is system. If d pinacoidal lel to the the miner, then it is the basal he monoclinic amphiboles, e 2 equivalent tions, they nsidered to be atic cleav-

3 symmetry sider in the

The Monoclinic System 3 Classes: Domatic Sphenoidal Prismatic

Axial Configuration: Three axes, all unequal in length, axes a and b intersect at an oblique angle labeled ß. The third axis, b, is perpendicular to the other two axes.

c -a b

ß

-b a

-c

180 Minerals from unknown or uncertain class: Aliettite Clinoptilolite-K Girdite Anthonyite Clinoptilolite-Na Glucine Apachite Clinotobermorite Grandviewite Ardaite Clinoungemachite Greenalite Artinite Coconinoite Griffithite Arzakite Coiraite Heulandite-Ca Balavinskite Cousinite Heulandite-Na Barahonaite-(Al) Dadsonite Heulandite-Sr Barahonaite-(Fe) Decrespignyite-(Y) Hisingerite Bariumbannisterite Denisovite Hochelagaite Bartelkeite Douglasite Hydrobasaluminite Bearsite Dypingite Hydrombobomkulite Berdesinskiite Earlandite Ikaite Brewsterite-Ba Eggletonite Ilmajokite Brumadoite Ernstite IMA2007-010 Buddingtonite Eugsterite IMA2008-022 Burckhardtite Eztlite Imogolite Caichengyunite Falkmanite Indigirite Calcurmolite Feinglosite Irhtemite In the 2/m symmetry class, ther confuse the issue, most Caryopilite Isoclasite however, there are 2 types Ferrisurite newer textbooks call the of forms, pinacoids and pinacoid form Jachymovite a paralleloCebaite-(Ce) Ferrosaponite prisms. Remember that a hedron. So we have 3 names pinacoid form consists of 2 Fervanite in recent literature for the Cebaite-(Nd) Jinshajiangite parallel faces (open form). Foshallasite same thing. Jonassonite Chistyakovaite-(Y) Let’s first look at a drawThe a pinacoid is also ing to show you where the Churchite-(Dy) Kaatialaite called the front (used to beFranconite mirror plane is and the oricalled the orthopinacoid), entation of the 2-fold rotaChurchite-(Nd) Gatumbaite Kankite the b is called the side tional axis (fig. 7.3). Churchite-(Y) Gearksutite Karpinskite pinacoid (used to be called the clinopinacoid), and the As described above, the b Kegelite rotation c is termed Clinobirnessite the basal pina- Gilalite axis is the 3-fold coid. axis. Clinochrysotile Giorgiosite Kenyaite

There are 2 additional pinacoids with the general form notations of {h0l} and {-h0l}. The presence of one of these forms does not necessitate the presence of the other one. These 3 pinacoids together form the diametrical prism

The 4-faced prism {hkl} is the general form. A monoclinic prism is shown in Figure 7.4. The general form can occur as two independent prisms {hkl} and {-hkl}. There are also {0kl} and {hk0} prisms. The {0kl} prism intersects the b and c axes and is parallel to the a axis.

Kitaibelite Kleemanite Kluchevskite Kogarkoite Kolovratite Kulkeite Kyzylkumite Lausenite Lavrentievite Lepidolite Lotharmeyerite Loudounite Luddenite Lunijianlaite Magadiite Maufite Maxwellite Melkovite Mendozavilite which is fixed by making th Middendorfite b axis the axis of 2-fold rotation is the b pinacoid Misenite {010}. Either of the other 2 axis may be chosen as c Montanite or a! Moraesite As an example, the {100} Mourite pinacoid, the {001} pinacoid, and the {h0l} pinaMundrabillaite coids may be converted into Museumite each other by simply rotating their orientation about Nahpoite the b axis! Corollary to +this situation, the prisms

may be interchanged in the same manner. We now need to look at some illustrations 31 of some relatively common monoclinic minerals. In these drawings you should recognize the letter notation where a, b, and c are the pinacoid forms (the dia metrical prism, remember?); m is the unit prism and z

exagonal system in article , we are ready to resume ur task of the removal of ymmetry from 3-axis sysems. Consider the axial ross, consisting of the a, , and c axes (each of unqual length), of the Monolinic System (fig. 7.1). In ll previous 3-axes systems, e considered what happens hen we vary one or more of he axial lengths, retainng the axial angles at 90 egrees to each other. But n the Monoclinic System, e will look at what hapens when we have 3 axes f unequal length and vary he angle off of 90 degrees etween two of the axes. Obiously, we must again lose ome symmetry! he axes are designated as ollows: the inclined axis s a and slopes out of the aper towards the viewer, he vertical axis is c, and he remaining axis which is t right angle to the plane f the a and c axes is b. hen properly oriented, the nclined axis a slopes toard the observer, b is horzontal and c is vertical. oth b and c axes are in the lane of the paper. n Figure 7.1, the angle etween c and b remains 90 egrees and the angle (^)

we will vary. Its called beta and is represented by the Greek letter in the axial figure. For most monoclinic crystals, the ^ beta is greater than 90 degrees, but in some rare instances, the angle may be 90 degrees. When this occurs, the monoclinic symmetry is not readily apparent from the morphology. The 2-fold rotation axis (the direction perpendicular to the mirror plane) is usually taken as the b axis. Then the a axis is inclined downward toward the front in the figure. Calculations of axial ratios in orthogonal crystal systems (where all the axes are perpendicular to each other) are relatively easy, but become quite tedious in systems with one or more inclined axes. I suggest an advanced mineralogy text, not an introductory one, if you ever get involved in something like this. Not even your standard mineralogy texts these days give the formulae to do these calculations. Aside from the axial constants necessary to describe minerals in the monoclinic system, the ^ beta must also be given. Given this situation, you might wish

Domatic

86 minerals from the Domatic Class:

Alsakharovite-Zn Antigorite Arakiite Ardealite Arrojadite Arrojadite-(BaFe) Arrojadite-(BaNa) Arrojadite-(KFe) Arrojadite-(KNa) Arrojadite-(NaFe) Arrojadite-(PbFe) Arrojadite-(SrFe)

Bafertisite Berthierine Bismutoferrite Bonattite Bornemanite Brianroulstonite Calcioancylite-(Nd) Canaphite Cervandonite-(Ce) Chapmanite Clinohedrite Dickinsonite

for orthoclase in a standard mineralogy textbook, like Klein and HurlbutĂ­s Manual of Mineralogy after E. S. Dana. You will find that for orthoclase a:b:c = 0.663:1: 0.559. ^beta = 115 degrees, 50 minutes. Cleavage is important to consider in this system. If there is a good pinacoidal cleavage parallel to the b axis (as in the mineral orthoclase), then it is usually called the basal cleavage. In the monoclinic pyroxenes and amphiboles, where there are 2 equivalent cleavage directions, they are usually considered to be vertical prismatic cleavages. There are only 3 symmetry classes to consider in the monoclinic system: 2/m, m, and 2. In the 2/m symmetry class, however, there are 2 types of forms, pinacoids and prisms. Remember that a pinacoid form consists of 2 parallel faces (open form). The a pinacoid is also called the front (used to be called the orthopinacoid), the b is called the side pinacoid (used to be called the clinopinacoid), and the

Dickinsonite Dickite Dozyite Endellite Eskimoite Ferri-arrojadite-(BaNa) Fluorarrojadite-(BaFe) Fluorarrojadite-(BaNa) Fluorarrojadite-(KNa) Fluorcanasite Fraipontite Furutobeite

Gerstleyite Gutkovaite Halloysite IMA2008-024 IMA2008064 Kampfite Kuzmenkoite Laffittite Langite Lepkhenelmite +

Sphenoidal

81 minerals from the Sphenoidal Class:

32

Afwillite Alflarsenite Amicite Armstrongite Barytocalcite Basaluminite Bermanite Bijvoetite-(Y) Boltwoodite Brabantite Brindleyite Bykovaite

Calcioferrite Camerolaite Campigliaite Chalcoalumite Chekhovichite Chromceladonite Clinobehoite Crawfordite Cymrite Englishite Fergusonite-beta-(Ce) Fettelite

Fichtelite Franklinfurnaceite Goosecreekite Halotrichite Hydrocalumite Joaquinite-(Ce) Kingsmountite Koragoite Krautite Larisaite Latiumite Levyclaudite

Lithosite Liveingite Marumoite Mesolite Metaheinrichite Metauranocircite Mosandrite Nickelalumite Omongwaite Orlovite Paradocrasite +

coid. There are 2 add pinacoids with al form notatio and {-h0l}. The one of these fo necessitate the the other one. These 3 pinacoi form the diamet (fig. 7.2), whi analogue of the isometric syste ther confuse th newer textbooks pinacoid form a hedron. So we h in recent liter same thing. Let’s first loo ing to show you mirror plane is entation of the tional axis (fi As described ab axis is the 3-f axis. The 4-faced pri the general for clinic prism is Figure 7.4. The form can occur dependent prism {-hkl}. There a and {hk0} prism prism intersect axes and is par a axis.

ditional the generons of {h0l} e presence of orms does not e presence of

ids together trical prism ich is the e cube in the em. To furhe issue, most s call the a parallelohave 3 names rature for the ok at a drawu where the s and the orie 2-fold rotaig. 7.3). bove, the b fold rotation ism {hkl} is rm. A monos shown in e general as two inms {hkl} and are also {0kl} ms. The {0kl} ts the b and c rallel to the

only form in the 2/m class which is fixed by making the b axis the axis of 2-fold rotation is the b pinacoid {010}. Either of the other 2 axis may be chosen as c or a! As an example, the {100} pinacoid, the {001} pinacoid, and the {h0l} pinacoids may be converted into each other by simply rotating their orientation about the b axis! Corollary to this situation, the prisms may be interchanged in the same manner. We now need to look at some illustrations of some relatively common monoclinic minerals. In these drawings you should recognize the letter notation where a, b, and c are the pinacoid forms (the diametrical prism, remember?); m is the unit prism and z is a prism; o, u, v, and s are pyramids; p, x, and y are orthodomes; and n is a clinodome.

Prismatic

Figures 7.5a, b, and c are common forms for the mineral orthoclase and 7.5d is a common form for selenite (gypsum). Many common minerals crystallize in this symmetry class, including azurite, clinopyroxene and clinoamphibole groups,

malachite, orthoclase, realgar, titanite, spodumene, and talc. The second monoclinic symmetry class is m and represents a single vertical mirror plane (010) that includes the c and a crystallographic axes. A dome is the general form {hkl} in this class (fig. 7.6) and is a 2-faced figure that is symmetrical across a mirror plane. There are 2 possible orientations of the dome, {hkl} and {-hkl). The form {010} is a pinacoid, but all the faces on the other side of the mirror plane are pedions. These include {100}, {- 100}, {001), and {h0l}. Only 2 rare minerals, hilgardite and clinohedrite, crystallize in this class. The third monoclinic symmetry class is 2 and represents a 2-fold axis of rotation on the b crystallographic axis. Figure 7.7 represents the general {hkl} form Ăą a sphenoid or dihedron. Since we have no a-c symmetry plane and with the b axis being polar, in the 2 symmetry class, we have different forms present at the opposite ends of b. The {010} pinacoid of 2/m be-

{0-10}. Likewise, the {0kl} {hk0} and {hkl} prisms of 2/m degenerate into pairs o right- and left-hand (enantiomorphic) sphenoids. The general form, the sphenoid, is enantiomorphic and has the Miller indices {hkl and {h-kl}. Mineral representatives are scarce for this class, but include the halotrictite group with the mineral pickeringite as the most commonly occurring mem ber. For comparisonĂ­s sake, take another look at Figure 7.6 and 7.7, just to keep straight what we are talkin about.

1281 minerals from the Prismatic Class:

Acanthite Actinolite Acuminite Admontite Aegirine Aegirine-augite Ahlfeldite Akaganeite Akrochordite Alacranite Alamosite Allactite Allanite-(Ce) Allanpringite Alleghanyite Allochalcoselite Alluaudite Alpersite Altisite Aluminite Aluminobarroisite Aluminoceladonite Aluminoferrobarroisite Aluminotaramite Alvanite Amarillite Ameghinite Ammonioborite Amstallite Anandite Andremeyerite Andyrobertsite Angelaite Ankinovichite Annabergite Annite Ansermetite Antimonpearceite Apatite Apjohnite Aplowite Aravaipaite Arfvedsonite Aristarainite Armbrusterite Arseniopleite Arseniosiderite Arsenopyrite Arsenpolybasite Arsentsumebite Arthurite Artsmithite Arupite

Aschamalmite Aspidolite Atelestite Attakolite Augelite Augite Aurichalcite Aurivilliusite Avdoninite Azurite Baddeleyite Baghdadite Bahianite Bakerite Bakhchisaraitsevite Balangeroite Bannermanite Bannisterite Barbosalite Bariandite Baricite Barnesite Barroisite Barstowite Barytolamprophyllite Bassetite Baumhauerite Bayerite Bayldonite Bayleyite Baylissite Bazhenovite Bearthite Beidellite Belloite Bementite Benavidesite Bendadaite Benjaminite Beraunite Bergenite Bergslagite Bernardite Berryite Beryllonite Betpakdalite Beusite Bianchite Bieberite Biehlite Bilinite Biotite Biraite-(Ce)

Biringuccite Bischofite Bismite Bityite Bjarebyite Bleasdaleite Blixite Blodite Bobfergusonite Bobierrite Bobjonesite Bobkingite Boggildite Bokite Bonshtedtite Boothite Boralsilite Borax Borcarite Borocookeite Borodaevite Boromuscovite Botallackite Botryogen Bouazzerite Boussingaultite Boyleite Brackebuschite Bradaczekite Brammallite Brandtite Brannerite Brazilianite Brendelite Brewsterite Brezinaite Brianite Brianyoungite Brinrobertsite Brochantite Brodtkorbite Bruggenite Brushite Burangaite Burgessite Burovaite-Ca Burpalite Bushmakinite Bussyite-(Ce) Butlerite Cabalzarite Cafetite Calaverite

Calcioandyrobertsite Calciogadolinite Calcjarlite Calclacite Calcybeborosilite-(Y) Calderonite Callaghanite Camgasite Canasite Canavesite Cannilloite Cannizzarite Cannonite Caracolite Carboborite Carlfriesite Carmichaelite Carnotite Caryinite Caryochroite Cassedanneite Catapleiite Celadonite Celsian Cerotungstite-(Ce) Chalcocite Chalconatronite Challacolloite Chamosite Changoite Charoite Chenevixite Cheralite-(Ce) Chernykhite Chervetite Chevkinite-(Ce) Chloromenite Chlorophoenicite Chloroxiphite Chondrodite Chopinite Chrisstanleyite Chromphyllite Chrysotile Chukanovite Chursinite Chvaleticeite Cianciulliite Ciprianiite Claudetite Clearcreekite Clinoatacamite +

33

Triclinic

34

The Triclinic System 2 Classes: Pedial Pinacoidal

Axial Configuration: Three axes labled a, b and c that are all unequal in length and intersect at three different angles labeled ß, ƒ and ø.

c -b

ß

-a ø

a

ƒ

b

-c 29 Minerals from unknown or uncertain class: Abelsonite Alstonite Anthoinite Baileychlore Bamfordite Barentsite Barringtonite Bauranoite Bukovskyite Calciouranoite Carlhintzeite Cejkaite Clairite Claraite Coyoteite Dorrite Ferrazite Ferristrunzite

Ferrolaueite Ferrostrunzite Franklinphilite Gartrellite Geminite Gerdtremmelite Gormanite Hotsonite-VI Howieite Hydroscarbroite Kamitugaite Kolwezite Korshunovskite Kribergite Lengenbachite Lennilenapeite Letovicite Mangazeite

Marsturite Mcnearite Metavanuralite Metavivianite Montroyalite Mpororoite Nasledovite Niobophyllite Oboyerite Okenite Otjisumeite Parabrandtite Phosphoinnelite Polyhalite Pseudojohannite Pushcharovskite Richetite Rodalquilarite

Roselite Rouseite Sanjuanite Scarbroite Sieleckiite Souzalite Svyazhinite Tavorite Tinaksite Triangulite Utahite Veatchite Wilcoxite Xenophyllite Zaherite Znucalite

35

Pedial

54 minerals Analcime Arhbarite Arsenopalladinite Astrophyllite Aubertite Axinite-(Mg) Bikitaite Bussenite Chabourneite Chaidamuite Chenite Donnayite Epistilbite Frankamenite

36

er systems, by looking at the axial cross of the Triclinic System (fig. 8.1). In this figure, we see that all 3 axes (a, b, and c) are unequal in length to each other and that there are no axial angles of 90 degrees. In the Monoclinic System, at least we had a and b axes at right angles, but here we have lost even that! Note that the angle beta is still between the c and a axes, but we now have 2 additional angles to define, neither of which are equal to 90 degrees. One angle is termed alpha and is defined as the angle between the c and b axes and the second is gamma which is defined as the angle between a and b. Now, we must have some accepted conventions or rules to follow to orient a triclinic crystal, or we will always be in a state of confusion with other folks over just the orientation. Remember, in the orientation of any crystal, you also are determining the position of the 3 crystallographic axes. So, the rules are: 1) the most pronounced zone should be vertical and therefore the axis in this zone becomes the c; 2) the {001}form (basal pinacoid) should slope forward and to the right; and 3) select two forms in the vertical zone, one will be the {100} and the other will be the {010}. Now, the direction of the a axis is determined by the intersection of {101} and {001} and the direction of the b axis is determined by the intersection of {100} and {001}. Once this is done, the a axis should be shorter than the b axis so that the convention becomes c < a < b. The axial distances and the 3 angles, alpha, beta, and gamma, can be calculated only with considerable difficulty. As in the Monoclinic system, the b axis length is defined as unity (1). The crystallography information concerning a triclinic mineral will the following (an example): a:b:c = from the Pedial Class: include 0.972: 1 : 0.778; alpha = 102 degrees 41 minbeta = 98 degrees 09 minutes, gamma = 88 Gilmarite Manandonite utes, Quadruphite-VIII degrees 08 minutes. Glagolevite Mcauslanite Sinnerite In the triclinic system, we have two symmeHartite Mohite Sobolevite try classes. The first we will consider is the (Hermann-Mauguin notation). In this class, Hilgardite Murmanite -1 there isTaneyamalite a 1-fold axis of symmetry, the equiva center of symmetry or inversion. Innelite Nefedovite alent ofTantite Iranite Nekoite Tridymite Figure 8.2 shows a triclinic pinacoid (or parallelohedron). This class is termed the pinaKaolinite Nickeltalmessite Tundrite-(Nd) coidal class after its general form {hkl}. So all the forms present are pinacoids and thereKatayamalite Nordstrandite fore consist Tyretskiteof two identical and parallel faces. Vaughanite Kristiansenite Paravinogradovite Kuliokite Petitjeanite When youVolkovskite orient a triclinic crystal, the Millindices of the pinacoid determine its posiKurgantaite Polyphite-VII er Weissbergite tion. There are 3 pinacoids. Leucophanite Polyphite-VIII Welshite Remember pinacoids intersect one axis and are Mackelveyite Pringleite parallel to the other 2 (in 3 axes systems). So let’s start by looking at the -1 symmeMaghrebite Quadruphite-VII try. This is a one-fold axis of rotoinversion, which may be viewed as the same as having a center of symmetry. Figure 8.3 shows a triclinic pinacoid, also called a parallelohedron. This class is referred to as the pinacoidal class, due to its {hkl} form. With -1 symmetry, all forms are pinacoids so they consist of 2 identical parallel faces. Once a triclinic crystal is oriented, then the Miller indices of the pinacoid establish its position. Figure 8.3 Triclinic pinacoids, or parallelohedrons There are 3 general types of pinacoids: those that intersect only one crystallographic axis, those that intersect 2 axes, and those that intersect all 3 axes. The first type are the pinacoids {100}, {010}, and {001}. The {100} is the front pinacoid and intersects the a axis, the {010} is the side or b pinacoid and intersects the b axis, and the {001} is the c or basal pinacoid and intersects the c axis. All of these forms are by convention based on the + end of the axis. The second type of pinacoid is termed the {0kl}, {h0l}, and {hk0} pinacoids, respectively. The {0kl} pinacoid is parallel to the a axis and therefore intersects the b and c axes. It may be positive {0kl} or negative {0kl}. The {h0l} pinacoid is parallel to the b axis and intersects the a and c axes. It may be positive {h0l} or negative {-h0l}. Finally, the {hk0} pinacoid is parallel to the c axis and intersects the a and b axes. It may be positive {hk0} or negative {h-k0}. The third type of pinacoid is the {hkl}. There exist positive right {hkl}, positive left {hkl}, negative right {-hkl}, and negative left {-h-kl}. Each of these 2-faced forms may exist independently of the others. Figure 8.3 shows some of the pinacoidal forms in this class. A number of minerals crystallize in the -1 class including plagioclase feldspar pectolite, microcline, and wollastonite. The second symmetry class of the triclinic system is the 1, which is equivalent to no symmetry! It is a single face termed a pedion and the class called the pedial class after its {hkl} form. Because the form consists of a single face, each pedion or monohedron stands by itself. Rare is the mineral that crystallizes in this class, axinite being an example.

Pinacoidal

317 minerals from the Pinacoidal Class: Abramovite Adamsite Aenigmatite Agrellite Aheylite Ajoite Akatoreite Albrechtschraufite Althupite Aluminocopiapite Alumohydrocalcite Alunogen Amarantite Amblygonite Anapaite Andesine Angastonite Angelellite Anorthite Anorthoclase Anorthominasragrite Aramayoite Artroeite Atencioite Aurorite Axinite-(Fe) Babingtonite Batisivite Baumhauerite Baumstarkite Bellingerite Braithwaiteite Britvinite Bultfonteinite Bustamite Bytownite Calcioaravaipaite Calciocopiapite Caoxite Carboirite-III Carboirite-VIII Cascandite Cassidyite Cattiite Ceruleite Chabazite-Ca Chalcanthite Chalcosiderite Chloritoid Christelite Chudobaite Cobaltkoritnigite Cobaltneustadtelite

Coeruleolactite Collinsite Copiapite Coquandite Cornubite Cuprocopiapite Cuprosklodowskite Cylindrite Dalyite Davanite Deanesmithite Dellaite Demesmaekerite Diadochite Doyleite Ehrleite Emmonsite Epistolite Ershovite Ezcurrit Fairbankite Fairfieldite Faizievite Faustite Fedorite Fenaksite Ferrarisite Ferricopiapite Ferrobustamite Fiedlerite Fingerite Florkeite Fluckite Footemineite Franckeite Frolovite Furongite Gabrielite Gageite Gaitite Galgenbergite Geigerite Gerenite Goldquarryite Gordonite Gotzenite Hainite Hallimondite Hannayite Hatchite

Helmutwinklerite Hemihedrite Hemloite Heneuite Henmilite Hillite Hiortdahlite Hogtuvaite Hohmannite Howardevansite Hubeite Huemulite Hummerite Hungchaoite Hyalotekite Hydroastrophyllite Hydrodresserite Iimoriite IMA2008-010 IMA2008-046 IMA2008-048 IMA2009-008 IMA2009-010 IMA2009-011 IMA2009-016 Incaite Inesite Jagowerite Jamesite Jankovicite Jennite Johannite Johninnesite Jokokuite Juabite Kalifersite Kapitsaite Kastningite Keldyshite Kermesite Kingite Koritnigite Krinovite Kupletskite Kurnakovite Kyanite Labradorite Lalondeite Laueite Lindackerite Lishizhenite Lithiomarsturite Litidionite

Lizardite Lomonosovite Lopezite Ludjibaite Ludlockite Ludlockite Lukrahnite Lulzacite Luneburgite Magnesioaubertite Magnesiocopiapite Makarochkinite Manaksite Manganbabingtonite Mangangordonite Marecottite Margarosanite Martinite Mcbirneyite Mckelveyite Medenbachite Melanovanadite Meridianiite Messelite Metadelrioite Metahohmannite Metakottigite Metarauchite Metarossite Meyerhofferite Microcline Minnesotaite Miserite Mitryaevaite Monetite Montbrayite Montebrasite Mounanaite Nacaphite Nalivkinite Nambulite Natromontebrasite Natronambulite Nealite Nealite Neustadtelite Niobokupletskite Oligoclase Orlandiite Osakaite Paganoite +

37