2.7" Garnet, Diopside, Epidote & Biotite Association - Afghanistan

Diopside is a pyroxene mineral with the chemical formula MgCaSi₂O₆. It is often found as small green crystals within metamorphic and igneous rocks, though it can vary in color including yellow, brown and black crystals. It is an important indicator rock when searching for deep-source volcanic pipes that may or may not contain diamonds. Geologists that are searching for these pipes often look for diopside crystal fragments since they form in nearly the same atmospheric conditions and locations as diamonds. Diopside crystals with deep green coloration are known as chrome diopside.

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. There are three varieties of andradite which include melanite (black garnets), topazolite (yellow garnets) and demantoid (green garnets). It occurs in skarns developed in contact metamorphosed impure limestones or calcic igneous rocks; in chlorite schists, serpentinites and in alkalic igneous rocks (typically titaniferous).

Garnets are nesosilicates having the general formula X3Y2(SiO4)3. There are many species of garnet which include pyrope, almandine, spessartine, uvarovite, andradite and grossular (varieties of which are hessonite, cinnamon-stone and tsavorite). Garnets are found in a wide variety of colors including red, orange, yellow, green, purple, brown, blue, black, pink, and colorless, with reddish shades being the most common.

Epidote is a green, silicate mineral that is commonly found in regionally metamorphosed rocks. It often forms lustrous, elongated and interconnected crystals that are highly coveted by collectors. While nearly all epidote is green it may take on many different shades and tones from yellowish to deep green.