Smokey Quartz
Smokey Quartz is a brown-black gem variety of quartz, belonging to the rock crystal family of stones. All rock crystals are composed of SiO2 They form according to a trigonal crystal structure, and have a hardness of 7 on the Mohs scale.
Citrine
Formula: SiO2 Colour: Yellow – Orange Lustre: Vitreous Hardness: 7 Crystal System: Trigonal
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