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Biotite
Biotite - Mineral Properties and Uses |
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What is Biotite? |
Biotite is a common rock-forming mineral. It is a mica found in many types of igneous rocks and in some metamorphic rocks. It is easily recognized because of its perfect cleavage that allows it to separate into thin, black, flexible sheets. |
Uses |
Biotite has very limited commercial use. Biotite particles are sometimes used as a surface treatment in decorative concrete, plaster and other construction materials. It is also used in the potassium-argon method for dating igneous rocks. |
Color |
black, dark green, dark brown |
Streak |
white to gray |
Luster |
vitreous |
Diaphaneity |
transparent to translucent |
Cleavage |
basal, perfect |
Hardness |
2.5 - 3 |
Specific Gravity |
2.7 - 3.3 |
Distinguishing
Characteristics |
dark color, perfect cleavage |
Crystal System |
monoclinic |
Chemical Classification |
silicate |
Chemical Composition |
K(Mg,Fe)3(Si3Al)O10(OH,F)2 |
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Biotite from Bancroft, Ontario, Canada.
Specimen is approximately 4 inches (10 centimeters) across.
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Biotite from Bancroft, Ontario, Canada.
Specimen is approximately 4 inches (10 centimeters) across.
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Cut biotite from Bancroft, Ontario, Canada.
Specimen is approximately 4 inches (10 centimeters) across.
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A side view of biotite from Bancroft, Ontario, Canada.
Specimen is approximately 3/8 inch (.95 centimeter) thick.
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Mineral photographs that appear on this page with a Geology.com copyright mark are property of Geology.com and may not be used beyond our website. If you like these photos and would like to share them with others please link to this page or email its URL. The photos were taken and composed by Ann Bryant.
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