Biotite is a common class of sheet silicate mineral belonging to the mica group. It is characterized by its dark brown to black color, although some variations can appear green or even transparent. Biotite is formed as a result of the crystallization of magma during igneous rock formation, or through metamorphic processes involving the alteration of existing minerals.
In terms of its physical properties, biotite possesses a distinct platy or flaky structure, with thin and flexible sheets that can be easily separated. It has a vitreous to pearly luster and exhibits a characteristic perfect basal cleavage, allowing it to be split into thin sheets. The mineral also has a hardness of 2.5 to 3.0 on the Mohs scale, making it relatively easy to scratch. Biotite typically has a high refractive index, resulting in a strong pleochroism where it displays different colors when viewed from different angles.
Due to its abundance and widespread occurrence, biotite is utilized in various applications. It serves as an essential indicator mineral in geology, helping geologists identify the composition and age of rocks. Biotite is also employed in the manufacturing of certain electrical insulators and capacitors due to its dielectric properties. Furthermore, it can be used as a pigment in paints and cosmetics. Additionally, biotite often serves as a valuable source of potassium, which is extracted from the mineral for use as fertilizer in agriculture.
The word "biotite" is derived from the French word "biot", which refers to a French mineralogist named Jean-Baptiste Biot. Biotite is a type of sheet silicate mineral belonging to the mica group. Its name was coined by the German mineralogist Karl Ludwig von Fuchs in 1826, in honor of Biot's contributions to the field of mineralogy.