The Mineral, Biotite is a member of the Mica Group of minerals. Typically, Biotite is found in laminar masses or disseminated scales. It has a hardness of 2.5, SG of 2.7 to 3.2, can be brown, black, greenish or transparent/opaque. This particular specimen is light brown to gray on the sides and highly reflective on the top and bottom, mirror like. Biotite is, perhaps, the most common of the micas.