2.5" Andradite on Hedembergite - Greece

 

Andradite is a species of the garnet group, and although not as well-known as some other types of garnets, such as Almandine or pyrope, it is the most lustrous. It tends to be opaque, so most andradite is not gemstone-quality. It occurs in skarns developed in contact-metamorphosed impure limestones or calcic igneous rocks; in chlorite schists and serpentinites; and in alkalic igneous rocks, often titaniferous.

Andradite comes in three varieties: melanite, colored by titanium substitutions for iron in its formula; topazolite, a rare and yellow-green variety; and demantoid, a striking green variety that is one of the world's rarest and most valuable gemstones.

Recently, rich deposits of andradite and grossular garnets have been discovered in contact-metamorphic deposits in the Republic of Mali. This find is one of the largest garnet deposits that produces commercial amounts of material.