Biotite mainly occurs in metamorphic rocks, granite and other rocks. The color of biotite is from black to brown or green, with glass luster. The shape is plate and column. In recent years, biotite has been widely used in stone paint and other decorative coatings.
The single crystal of biotite is short columnar and plate-shaped, with a hexagonal cross-section and scaly aggregate. Brown or black. The color becomes darker with the increase of iron content. Other optical and mechanical properties are similar to those of muscovite, with a relative density of 2.7-3.3.