Andradite Garnet

Andradite includes three varieties:

Melanite: Black in color, referred to as "titanian andradite".

Demantoid: Vivid green in color, one of the most valuable and rare stones in the gemological world.

Topazolite: Yellow-green in color and sometimes of high enough quality to be cut into a faceted gemstone, it is rarer than demantoid.

It occurs in skarns developed in contact metamorphosed impure limestones or calcic igneous rocks; in chlorite schists and serpentinites and in alkalic igneous rocks (typically titaniferous). Associated minerals include vesuvianite, chlorite, epidote, spinel, calcite, dolomite and magnetite. It is found in Italy, the Ural Mountains of Russia, Arizona and California and in Dnipropetrovsk Oblast in Ukraine. Like the other garnets, andradite crystallizes in the cubic space group [[Ia3d]], with unit-cell parameter of 12.051 Å at 100 K. The spin structure of andradite contains two mutually canted equivalent antiferromagnetic sublattices below the Néel temperature (TN=11 K).

Andradite Garnet is a garnet which makes it a birthstone for those born in January.