The Mineral magnesiochromite

Magnesiochromite is very similar to Chromite, and is often mistaken for it. Due to their similarity, it is very difficult to visually distinguish these two minerals. Magnesiochromite is the magnesium-dominating form in a series with Chromite, whereas Chromite is iron-dominating.

Chemical Formula

MgCr₂O₄

Color

Black to brownish-black

Crystal System

Isometric

Properties

Streak Dark gray

Hardness 5.5

Transparency Opaque

Specific Gravity 4.2

Luster Metallic to dull

Cleavage None

Fracture Conchoidal to uneven

Tenacity Brittle

Crystal Habits

Crystals, which are octahedral, are very rare. Usually grainy, massive, and as rounded embedded masses.

3D Crystal Atlas

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Additional Information

Composition Magnesium chromium oxide, often with some iron.

In Group Oxides; Multiple Oxides

Striking Features Streak and hardness

Environment In Serpentine deposits, as well as in ultrabasic igneous rocks. May also be in placer deposits.

Rock Type Igneous, Metamorphic

Other Names

Picrochromite

Noteworthy Localities

Magnesiochromite does not have well defined localities, as it occurs scattered in chrome deposits together with Chromite. The type locality for this mineral is Schwarzenberg, in the Erzgebirge, Saxony, Germany. Other occurrences are the Saranovskoye Mine, Sarany, Ural Mountains, Russia; Soldiers Delight, Owings Mill, Baltimore Co., Maryland; and the Cedar Mountain Ridge Chromite deposit, near Livermore, Alameda Co., California.

Common Mineral Associations

Chromite, Serpentine, Clinochlore, Magnetite, Uvarovite

Distingushing Similar Minerals

Chromite - Has a brownish streak, is slightly attracted to magnetic fields.

magnesiochromite Photos

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