What is Chromite?
Chromite is associate degree chemical compound
mineral composed of Cr, iron, and chemical element (FeCr2O4). It’s dark grey to
black in color with an auriferous to submetallic luster and a high relative
density. It happens in basic and ultra basic igneous rocks and within the
metamorphic and substance rocks that are made once chromite-bearing rocks are
altered by heat or weathering.
 |
| Raw Chromite Ore |
Chromite is vital as a result of it's the sole
economic ore of Cr, a vital component for a good sort of metal, chemical, and
made merchandise. Several different minerals contain Cr, however none of them are
found in deposits which will be economically strip-mined to provide Cr.
Properties of Mineral
Chromite may be difficult to spot. Many properties should be thought-about to differentiate it from different auriferous ores. Hand specimen identification of mineral needs a thought of: color, relative density, luster, and a characteristic brown streak. The foremost vital clue to distinguishing mineral is its association with ultra basic igneous rocks and metamorphic rocks like serpentine.
 |
| Chromite Mineral Isolated |
Chromite is typically slightly magnetic. This
could cause it to be confused with magnetic iron-ore. Mineral and mineral have
terribly similar properties. Careful observations of hardness, streak, and
relative density are needed to tell apart these minerals in hand specimens.
|
Physical
Properties of Chromite |
|
|
Chemical
Classification |
Oxide |
|
Color |
Dark
gray to black, rarely brownish black |
|
Streak |
Dark
brown |
|
Luster |
Metallic
to submetallic |
|
Diaphaneity |
Opaque |
|
Cleavage |
None |
|
Mohs Hardness |
5.5
to 6 |
|
Specific Gravity |
4.0
to 5.1 (variable) |
|
Diagnostic
Properties |
Luster,
streak |
|
Chemical
Composition |
FeCr2O4
with magnesium substituting for iron in significant amounts |
|
Crystal System |
Isometric |
|
Uses |
An
ore of chromium |
Chromite and primary solid solution :
Magnesium oftentimes substitutes for iron in mineral. A primary solid solution series exists between the mineral mineral (FeCr2O4) and therefore the similarity mineral magnesiochromite (MgCr2O4). Intermediate specimens may be made in iron ((Fe, Mg) Cr2O4) or metal (Mg, Fe) Cr2O4). For convenience in communication, these minerals are typically cited together as "chromite."
Some mineralogists provides a generalized chemical
composition of (Mg, Fe) (Cr, Al) 2O4 for mineral. This composition acknowledges
multiple primary solid solution ways between mineral and hercynite (FeAl2O4),
mineral (MgAl2O4), magnesiochromite (MgCr2O4), magnetic iron-ore (Fe3O4), and
magnesioferrite (MgFe2O4).
 |
| Unpolished Chromite Rock Isolated |
Because of the numerous completely different
compositions in these primary solid solution series, geologists and
metallurgists typically take into account "chromite" to be any member
of the primary solid solution series that contains a vital Cr2O3 content.
Stratiform, Podiform, and Beach Sands
Small amounts of mineral are found in many sorts
of rock. However, mineral deposits that are giant enough for mining are usually
found in: 1) stratiform deposits (large plenty of rock like no rite or igneous
rock that slowly crystallized from submerged magma); 2) pod form deposits
(serpentines and different metamorphic rocks derived from the alteration of
norite and peridotite); and, 3) beach sands (derived from the weathering of
chromite-bearing rocks).
STRATIFORM DEPOSITS
Stratiform deposits are giant plenty of rock that
cooled terribly slowly in submerged rock chambers. Throughout this slow
cooling, mineral and associated minerals crystallized early whereas the rock
was still at a really extreme temperature. Their crystals then settled to very
cheap of the rock chamber to create a stratified deposit. A number of the
layers in these deposits will contain five hundredth or additional mineral on
the premise of weight.
Most of the world's better-known mineral happens
in 2 stratiform deposits: the Bushveld complicated in Republic of South Africa
and therefore the nice Dyke in African nation. Different vital stratiform
deposits include: the Stillwater complicated in American state, the Kemi complicated
of European nation, the Orissa complicated of Asian country, the Goias in
Brazil, the Mashaba complicated of African nation and tiny deposits in
Madagascar. Nearly all of those are aeon in age.
PODIFORM DEPOSITS
Podiform deposits are giant slabs of oceanic layer
that are thrust up onto a continental plate. These slabs of rock additionally
referred to as "ophiolites," will contain vital amounts of mineral.
In these deposits the mineral is disseminated through the rock and not
extremely targeted in easy-to-mine layers. Podiform deposits are better-known
in Kazakhstan, Russia, the Philippines, Zimbabwe, Cyprus, and Greece.
The first discoveries of podiform mineral deposits
were created close to Baltimore, Maryland within the early 1800s. These
deposits provided nearly all of the world's mineral till concerning 1850. These
deposits were tiny and aren't any longer in production.
BEACH SANDS
Chromite is found in beach sands derived from the
weathering of chromite-bearing rocks and dirt soils that developed over igneous
rock. Beach sand made in mineral and different significant minerals is
typically strip-mined, processed to get rid of significant minerals, and came
to the setting.
Two facts permit these mineral sands to often
contain economic deposits of mineral. First, mineral is one amongst the
additional weathering-resistant minerals of igneous rock. That causes it to be
targeted in residual soils that type within the weathering zone higher than
chromite-rich rocks. Second, mineral contains a higher relative density than
different minerals in igneous rock. This causes it to be by selection
transported and deposited by wave and current actions, concentrating it in sure
locations at streams and beaches. These deposits are typically made enough and
enormous enough that they will be strip-mined for mineral.
Uses of mineral and Cr
Chromium may be a metal accustomed induce
hardness, toughness, and chemical resistance in steel. The alloy made is
thought as "stainless steel." once alloyed with iron and nickel, it
produces associate degree alloy referred to as "nichrome" that is
proof against high temperatures and accustomed create heating units, ovens, and
different appliances. Skinny coatings of Cr alloys are used as platings on
motorcar components, appliances, and different merchandise. These are given the
name "chrome plated." it's additionally accustomed create superalloys
which will perform well within the hot, corrosive, and high-stress setting of
jet engines.
Chromium's name comes from the Greek word
"chroma" which suggests "color." Cr is employed as a
pigment in paint. The acquainted yellow lines painted down the middle of
highways and therefore the yellow paint used on faculty buses ar typically "chrome
yellow" - a color made from Cr pigment. Cr is a vital pigment in many
sorts of paint, ink, dye, and cosmetics. Trace amounts of Cr turn out the
colour in several minerals and gemstones. The red color of ruby, the pink of
some sapphires, and therefore the inexperienced color of emerald ar caused by
small amounts of Cr.
Chromite and Diamond Exploration
Kimberlite, the sort of rock that holds several of
the worlds most vital diamond deposits, typically contains tiny amounts of
mineral, ilmenite, and sure sorts of mineral. Though these minerals occur in
terribly tiny amounts, they're rather more common within the rock than
diamonds. As a result of these minerals don't occur along in most different
sorts of rocks, they will be a valuable indicator of a close-by peridotite body
if they're found in stream sediments, glacial tills, residual soils, core
samples, or well cuttings. A number of the best diamond deposits on Earth were
discovered victimization the earth science of indicator minerals.