Biotit
- Biotit is a common phyllosilicate mineral within the mica group, known for its dark brown to black color and its sheet-like crystal structure. It is primarily composed of potassium, magnesium, iron, aluminum, silicon, and hydroxide ions. nounThe geologist identified the dark mineral in the rock sample as biotit.Biotit is often found in igneous and metamorphic rocks, such as granite and schist.