Uvarovite

Uvarovite is a chromium-rich garnet and the chromium-dominant endmember of the grossular garnet group. Its ideal chemical formula is Ca3Cr2Si3O12, representing a Ca-rich garnet where chromium substitutes for aluminum in the Y site of the garnet structure. Like other garnets, uvarovite crystallizes in the cubic system and forms isometric crystals, often appearing as well-formed dodecahedra.

Physical properties include a deep emerald to dark green color, frequently with a vivid, glassy luster. The mineral is transparent to translucent and has a hardness around 6.5 to 7 on the Mohs scale. It is isotropic in optical behavior due to its cubic symmetry, with a refractive index typically around 1.74. Specific gravity ranges roughly from 3.6 to 3.8 g/cm3. Crystals are commonly small but can be well-formed when found in suitable hydrothermal or metamorphic settings.

Occurrence and formation: Uvarovite forms in chromium-rich ultramafic rocks, such as serpentinites and other metamorphosed or metasomatized ferruginous rocks. It is often found with chromian spinel, magnetite, and other garnets. The mineral is relatively rare compared with other garnet varieties, and large, gem-quality crystals are uncommon.

Applications and nomenclature: Due to its striking green color, uvarovite is sometimes collected or cut as a gemstone, though its rarity limits widespread use. It is primarily of interest to mineral collectors and as a chromian endmember that helps define garnet chemistry and solid-solution series.