Bixbyite

Bixbyite is a manganese oxide mineral with the chemical formula Mn2O3. It crystallizes in the cubic system and is commonly found as reddish-brown isometric crystals or granular masses. Bixbyite is notable for adopting the bixbyite structure, a cubic arrangement shared by several sesquioxides such as In2O3.

Geologically, bixbyite forms as an oxidation product in manganese-rich ore deposits and in hydrothermal veins. It is typically found associated with other manganese oxides, including pyrolusite (MnO2) and hausmannite (Mn2+Mn3+3O4), as well as various manganese silicates in some localities.

The mineral is named after the town of Bixby, Oklahoma, United States, where the type locality is located. It is an accessory mineral in oxidized zones rather than a primary ore mineral, and it serves as an indicator of manganese mineralization and specific redox conditions in the rocks where it occurs.

In terms of properties, bixbyite is opaque with a vitreous to resinous luster and a reddish-brown to brick-red color. It is primarily of interest to collectors and researchers for its crystal chemistry and structure, as well as its role in understanding oxidation processes in manganese-bearing systems.