1. These point groups are assigned to the trigonal crystal system. 2. It forms green to deep blue-green trigonal crystals . 3. It forms a colorless to yellow trigonal crystal with a vitreous luster. 4. Quartz belongs to the trigonal crystal system. 5. It crystallizes in the trigonal crystal system. 6. Magnesite consists of white trigonal crystals . 7. It crystallizes in the trigonal crystal system, and are rhombohedral in shape, typically with curved and striated faces. 8. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. 9. It occurs as disseminations and masses of opaque, metallic light bronze to brassy yellow grains which crystallize in the trigonal crystal system. 10. The cancrinite group are minerals with hexagonal and trigonal crystal systems with various anions and cations located in cages within the main frame.
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