metamorphic
Blue Quartz (specifically Dumortierite Quartzite)
Silicon Dioxide (SiO2) with inclusions of Dumortierite (Al7BO3(SiO4)3O3)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: Sky blue to denim blue, Luster: Vitreous to waxy, Crystal Structure: Trigonal (massive form), Cleavage: None (conchoidal fracture), Specific Gravity: 2.62-2.85
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Physical properties
Hardness: 7 (Mohs scale), Color: Sky blue to denim blue, Luster: Vitreous to waxy, Crystal Structure: Trigonal (massive form), Cleavage: None (conchoidal fracture), Specific Gravity: 2.62-2.85
Formation & geological history
Formed through the regional metamorphism of quartz-rich sediments where boron-rich fluids are present, leading to the growth of fibrous dumortierite inclusions within the quartz matrix.
Uses & applications
Used primarily in lapidary work for cabochons, beads, and carvings; also used in ceramic production for spark plugs and laboratory porcelain due to its high silica content.
Geological facts
The blue color is NOT caused by trace elements in the quartz itself, but by the presence of tiny needle-like crystals of the mineral dumortierite embedded inside the quartz. It is often mistaken for sodalite or lapis lazuli, but it is much harder.
Field identification & locations
Identify in the field by its hardness (will scratch glass easily) and its characteristic denim-blue mottled color. Common locations include Brazil, South Africa, and the Mojave Desert in California, USA.
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