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Physical Properties of Biotite
Color |
Black |
| Luster |
Non-Metallic, Vitreous |
| Streak |
White or gray |
| Cleavage |
1 direction, perfect |
| Specific Gravity |
2.7 - 3.3 |
| Hardness |
2 - 3 |
| Distinguishing Characteristics |
Perfect mica cleavage, Black color |
Optical Properties of Muscovite
Color |
Brown to redish Brown |
| Pleochroism |
Strong, light brown to dark brown |
| Relief |
Moderate to high positve relief (n = 1.552-1.696) |
| Interference Colors |
Very high order colors, (Birefringence = 0.3 - 0.7), interference colors may be difficult to examine in strongly colored samples |
| Opical System |
Biaxial Negative |
| 2V Angle |
0 - 25 degrees |
| Distinguishing Characteristics |
perfect cleavage, strong pleochroism |
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