Biotite is named for the French mineralogist J. B. Biot. It forms over a wide range of conditions and all over the world. Biotite is commonly found in granites, pegmatites, diorites, peridotites and gabbros. It is also commonly found in regional and contact metamorphised rocks.
| K(Mg,Fe)3(AlSi3O10)(OH)2 |
|
| Phyllosilicate |
|
| Monoclinic |
|
| 2/m |
|
| 2.5-3 |
|
| 2.8-3.2 |
|
| {001} perfect |
|
| Uneven |
|
| Black, dark brown, green |
|
| Gray |
|
| Splendent |
|
| Transparent/translucent/opaque |
|
| Micaceous |
|
| Notable Localities: |
Ontario, Canada; Russia |
| Uses: |
Heat insulation |
Specimens:
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