Chiastolite
Chiastolite is a form of Andulasite known for its distinctive cross pattern of black on brown. The black color bands come from black particles of graphite pushed together by crystal growth of a geometric nature. Chiastolite is opaque in contrast to the transparent crystalline luster of pure andulasite.
| Chemical Formula | Al2SiO5 |
| Color | Brown,, black |
| Hardness | 7Â -Â 7.5 |
| Crystal System | Orthorhombic |
| Refractive Index | 1.62Â -Â 1.65 |
| SG | 3.1Â -Â 3.2 |
| Transparency | Transparent to opaque |
| Double Refraction | -0.01 |
| Luster | Vitreous |
| Cleavage | 2,1 |
| Mineral Class | Andalusite |
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