GEO 2163 Lecture Notes - Lecture 1: Allanite, Crystal System, Orthorhombic Crystal System
8 Jan 2018
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Document Summary
Andalusite has an orthorhombic 2/m 2/m 2/m crystal system with elongated prisms as its crystal habit. The mineral has two good prismatic (110) cleavages. The hardness of andalusite is 6. 5-7. 5, and its density is 3. 13-3. 16. The luster is vitreous, the crystals are translucent to opaque. The mineral can be found in many colors including white, grey and pink with a white streak. The mineral occurrence is as common as nodules and is in contact with metamorphic slates and schists. Kyanite has a triclinic bar1 crystal system with bladed, columnar crystals as its crystal habit. The luster of the mineral is vitrous to pearly and can be found in pale, blue, grey, white. Its streak is white and the mineral occurs in high grade mica. Sillimanite has an orthorhombic 2/m 2/m 2/m crystal system with acicular or fibrous crystal habit. The mineral has one good (010) cleavage that is parallel to long axis.
