roscoelite

Roscoelite is a vanadium mica, a silicate mineral with the chemical formula K(V,Al)2(AlSi3O10)(OH)2. It is a member of the mica group, characterized by its layered structure. Roscoelite typically appears as fine-grained, scaly aggregates, and its color can range from brown and yellowish-brown to greenish and dark green. It is a relatively rare mineral, often found in association with other vanadium-bearing minerals like vanadinite and carnotite.

The mineral was first described in 1870 and named in honor of Colonel Henry L. Roscoe, a prominent English chemist known for his work on vanadium. Roscoelite is primarily of economic interest as a source of vanadium, a metal valued for its use in steel alloys, catalysts, and batteries. Significant deposits of roscoelite have been found in various locations worldwide, including the United States (Colorado, Utah), Mexico, and China. Due to its fine-grained nature, extraction and processing of vanadium from roscoelite can be complex. It is not a mineral commonly encountered in mineral collections due to its typical massive, rather than crystalline, habit.