Definition of biotite in English:

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Pronunciation: /ˈbīəˌtīt/


A black, dark brown, or greenish black variety of mica, occurring in many igneous and metamorphic rocks.
Example sentences
  • Although dark minerals such as biotite and hornblende are usually present, giving the rock a speckled appearance, they are never abundant.
  • Quartz, feldspar, white mica and biotite are all major constituents.
  • All four samples are medium-grained, and comprise variable proportions of hornblende, feldspar and quartz with accessory biotite and titanite.


Mid 19th century: named after Jean Baptiste Biot (1774–1862), French mineralogist.

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