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