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Chromite

Mineral Facts:Chemical Formula: FeCr2O4 Oxide of iron and chromium,

Chromium oxide 68.0%.The iron

may be partly replaced by

magnesium and the chromium by

aluminum and ferric iron.

Colors: Black to brownish

black. Streak - Dark Brown

Hardness: .

Densit!: 4."

Clea#a$e: It has a conchoidal oruneen fracture and no distinct

cleaage.

Cr!stallo$ra%h!: &sometric'Habit OctahedralCrystals small and rare. Occurs in

octahedrons, but is commonly found

massie, haing a granular or

compact structure.

(uster:. !ea" submetallic luster,often faint.

O%tics: )*e+racti#e &nde, O%a/ue

 

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Com%osition' Structure and 0ssociated Minerals:# common constituent of peridotite roc"s and the serpentines deried from them. The

mineral is found not only as crystals embedded in the roc" mass, but also as nodules in

it and as eins traersing it. One of the first minerals to separate from a cooling roc"magma, and its large ore deposits are thought to hae been deried by such magmatic

differentiation. It is probably in all cases a segregation from the magma producing the

roc". #ssociated $ith chrysolite asbestos, serpentine, corundum, etc eing ery

durable, chromite occurs in detrital deposits and in a fe$ places the mineral occurs in

the form of sand on beaches.

&denti+ication and Dia$nosticsIt resembles magnetite and fran"linite in appearance. Chromite is easily distinguished

from all other minerals but picotite by its crystalli&ation and its reaction for chromium.

It is distinguished from picotite by its inferior hardness and its higher specific graity.

!hen finely po$dered and fused on charcoal $ith sodium carbonate gies a magnetic

residue. Imparts a green color to the borax and salt of phosphorus beads 'a test for

chromium(. It is usually nonmagnetic, but some specimens sho$ slight magnetism

because of the admixture of magnetite $ith chromite.

&ndustrial 1ses o+ ChromiteChromite is the sole source of the metal chromium, $hich is the chrome)iron alloy

employed in the manufacture of special grades of steel. Chromium salts are used in

tanning and as pigments and plating. The crude ore, mixed $ith coal)tar, "aolin,

bauxite, or some other ingredient, is molded into bric"s and burned, after $hich the

bric"s are used as linings in metallurgical furnaces. These bric"s stand rapid changes of temperature and are not attac"ed by molten metals.

It is $idely spread through serpentine roc"s at many places, notably in russa, #sia

*inor+ at anat and else$here in or$ay+ at -oln"ie, in hodesia+ in the northern

portion of e$ Caledonia+ at arious points in *acedonia+ in the /rals, ussia+ in

eluchistan and *ysore, India. The annual production of chromite in the $orld is large,

as it is an important industrial mineral. *aor producers currently include -outh

#frica, Tur"ey and India.

It is found at many locations but only sparingly in the /nited -tates. In the /nited

-tates the mineral is "no$n at seeral points in a belt of serpentine on the east side ofthe #ppalachian *ountains, and at many points in the oc"y *ountains, the -ierra

eada and the Coast anges. It has been mined at are 1ills, *aryland+ in -is"iyou,

Tehama and -hasta Counties, California+ in Conerse County, !yoming+ and in

Chester and 2ela$are Counties, 3ennsylania+ and+ in 454, some $as $ashed from

chrome sand at altimore, *aryland. -mall amounts $ere historically produced in the

certain states of the /-, including 3ennsylania, *aryland,orth Carolina *ontana,

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Oregon and California and !yoming.