ferrimontebrasite

Ferrimontebrasite is a rare mineral belonging to the montebrasite-type apatite group. Its chemical formula is ideally Fe2+3(PO4)2(OH)2, though it often contains other divalent cations like manganese and magnesium, as well as some ferric iron. It is characterized by its iron content, which distinguishes it from its manganese-rich analog, lithiophilite, and its aluminum-rich counterpart, montebrasite.

The mineral typically forms in pegmatites, often associated with lithium-bearing minerals and other phosphates. It can also be found in some metamorphosed sedimentary rocks. Crystals are usually prismatic or equant, and the color can range from pale pink to reddish-brown or even black, depending on the presence of impurities. Ferrimontebrasite has a vitreous to greasy luster and a hardness of around 5 on the Mohs scale, with a specific gravity of approximately 3.2 to 3.6.

It is a relatively stable mineral, but can alter to other phosphate minerals under certain geological conditions. While not a common ore mineral, ferrimontebrasite is of interest to mineral collectors and geologists studying the paragenesis of pegmatites and phosphate deposits. Its discovery and characterization contribute to our understanding of mineral diversity and the complex chemical processes occurring within the Earth's crust. It is named after the Brazilian locality where it was first described.