biotite
Iron-magnesium mica
Biotite is a dark brown or black mineral of the mica family, common in igneous and metamite rocks.
It occurs in thin, flexible sheets that flake easily.
Biotite is distinguished from other micas by its dark color, caused by high iron and magnesium content.
Geologists use it to date rocks and study their formation conditions.
Common pale mica
- sheetFlat rectangular material
- silicateOxygen-bound crystal compound
- cleavageTendency to split cleanly
- basalOf the foundation
laminae · flaky · booklets · crystal · potassium · magnesium · iron · aluminum
Platy-mineral metamorphic rock
- gneissFoliated metamorphic rock
- graniteIgneous rock, quartz-rich
- metamorphicUndergoing structural change
- igneousFormed from cooled magma
weathering · crystallization · plutonic · intrusive · diorite · alteration · petrography · extinction
muscovite
Common pale mica
- sheetFlat rectangular material
- silicateOxygen-bound crystal compound
- cleavageTendency to split cleanly
basal · laminae · flaky · booklets · crystal · potassium · magnesium · iron · aluminum · hydroxyl
schist
Platy-mineral metamorphic rock
- gneissFoliated metamorphic rock
- graniteIgneous rock, quartz-rich
- metamorphicUndergoing structural change
igneous · weathering · crystallization · plutonic · intrusive · diorite · alteration · petrography · extinction · foliation
dark
Absence of light
greenish · vitreous · opaque · hexagonal · tabular · prismatic · brittle · refractive
- mineralsquartz, marble, granite, limestone, sandstone
- black mineralsgraphite, obsidian, onyx, jet, galena
- micasmuscovite, margarite
- silicate mineralsolivine, garnet, hornblende, cordierite, vermiculite
- silicatessilica, silicate, silicates, quartz, pyroxene
- potassium mineralsarcanite, niter, saltpeter, potash, muscovite