heterosite

Heterosite is a rare phosphate mineral with the chemical formula (Fe3+,Mn3+)PO4. It is a member of the heterosite-purpurite series, where it represents the iron-rich end-member. The manganese-rich end-member is purpurite. Heterosite typically occurs as a secondary mineral in pegmatites and hydrothermal veins, often associated with lithium-bearing minerals.

Crystallographically, heterosite belongs to the triclinic crystal system. It is commonly found as small, irregular grains or masses, though well-formed crystals are uncommon. The color of heterosite ranges from reddish-brown to purplish-red, with a streak that is typically pale brown to reddish. Its hardness on the Mohs scale is around 4 to 5, and it has a relatively high specific gravity, typically between 3.4 and 3.9.

The mineral was first described in 1878 and named from the Greek words "heteros" meaning "other" and "lithos" meaning "stone," referring to its unusual composition. While not economically significant for its mineral content, heterosite is of interest to mineral collectors and geologists studying pegmatite formation and mineral paragenesis. Its presence can indicate specific geological conditions and the alteration of primary phosphate minerals.