Biotite Data

Biotite is a phyllosilicate (sheet silicate) mica mineral.

Pronunciation: BUY•oh•tight (accent on capitalized syllable)

Color: black, dark green, dark brown

Streak: --

Luster: splendent (very shiny)

Diaphaneity: translucent; may appear opaque in hand specimen

Hardness: 2.5-3

Specific gravity:2.8-3.2

Cleavage/fracture: 1 -- breaks in paper-thin flexible elastic sheets

Other distinguishing properties: The black color and thin elastic cleavage sheets are diagnostic; found in many types of igneous and metamorphic rocks.


Specimen Pictures


References

Klein, C., and Hurlbut, C.S., Jr., 1999, Manual of Mineralogy (after James D. Dana) [21st edition, revised]: New York, John Wiley & Sons, 682 p.

Los Angeles County Museum of Natural History, The Photo Atlas of Minerals: nhm.org/pam/


Return to the Minerals page.


The original content of these web pages is © 2002-2008 by Vince Cronin. It may be used for non-profit educational and research purposes only.