GEO 2163 Lecture 8: Orthosilicates and Disilicates
22 Dec 2015
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Document Summary
Andalusite: this mineral has an orthorhombic 2/m 2/m 2/m crystal system with large elongated prisms as its crystal habit. The mineral has two good prismatic cleavages at (110). It has a hardness of 6. 5 to 7. 5 with a specific gravity of 3. 1-3. 2. It usually has a vitreous luster with translucent to opaque crystals. It naturally occurs in nodules and is in heavy contact with metamorphic slates and schists. It can be found in white/gray to pink. Kyanite: it has a triclinic bar 1 crystal system with bladed, columnar crystals as its crystal habit. It only has one good cleavage at (010) and has a hardness of 4-5 with a specific gravity of 3. 5-3. 7. It has a vitreous to pearly luster and naturally occurs in light-blue/ grey-white with a white streak. This mineral usually occurs in high grade mica. Sillimanite: this mineral has an orthorhombic 2/m 2/m 2/m crystal system with acicular or fibrous crystal habit.
