Uvarovite

grossular

chromium

Formula: Ca3Cr2(SiO4)3
Nesosilicate (insular SiO4 groups), garnet group, chromium mineral
Uvarovite forms a complete solid solution with grossular Ca3Al2(SiO4)3. This is possible because the ionic radius of Al3+ (0.535 Å) is similar to that of Cr3+ (0.615 Å). The Cr3+ of uvarovite is only partially replaced by Fe3+ (ionic radius 0.64 Å), and there is not a similar complete solid solution with andradite Ca3Fe3+2(SiO4)3
Specific gravity: 3.77 to 3.81
Hardness: 6½ to 7
Streak: white
Colour: green, green-black
Solubility: Insoluble in water, hydrochloric, nitric and sulphuric acid
Environments:

Metamorphic environments

Uvarovite occurs in metamorphosed chromite deposits and in skarn.

At the Outokumpu mine, Finland, uvarovite is found in skarn and serpentinised sediments (Lauf p137).

At the Saranovskii mine, Perm district, Urals, Russia, uvarovite is quite common, filling cracks in the chromite ore, associated with calcite, chromium-rich amesite and other species (Lauf p137).

Common impurities: Al,Fe,Mg

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