Biotite is a common phyllosilicate mineral within the mica group, characterized by its dark color, typically black or brown. It has a layered structure, allowing it to easily split into thin sheets. Biotite is primarily composed of potassium, magnesium, iron, and aluminum, and it often contains other elements like silicon and oxygen. This mineral is commonly found in igneous and metamorphic rocks, such as granite and gneiss. Biotite plays a significant role in the rock cycle and is important for understanding geological processes. Its presence can indicate the conditions under which the rock formed.