2.9" Andradite Garnet Cluster with Fluorapatite - China

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.

Garnets are nesosilicates with the general formula X3Y2(SiO4)3. There are many species of garnet, including 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, though reddish shades are the most common.

Fluorapatite is the most common variety in the apatite group. It forms early in almost all igneous rock as small, microscopic crystals. It can display a wide variety of colors and can be confused with beryl, phenakite and milarite. Often forming bright, lustrous crystals with hexagonal faces and off-center terminations. They are found in vugs, often associated with quartz and calcite. Most complete crystals are around an inch in length, though larger crystals up to about 4 inches long have been found.