metamorphic
Blue Quartzite
Blue Quartzite (Primary mineral: Quartz, SiO2 with magnesio-riebeckite or crocidolite inclusions)
Hardness: 7 (Mohs scale); Color: Grayish-blue to deep sky blue; Luster: Vitreous to waxy; Structure: Granitoid/Non-foliated crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7
- Hardness
- 7 (Mohs scale)
- Color
- Grayish-blue to deep sky blue
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Grayish-blue to deep sky blue; Luster: Vitreous to waxy; Structure: Granitoid/Non-foliated crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High temperature and pressure cause quartz grains to recrystallize. The blue color is often due to the presence of microscopic inclusions of fibrous blue minerals like dumortierite or riebeckite.
Uses & applications
Used primarily as decorative stone, countertops, flooring, and in lapidary work for jewelry (cabochons) and carvings. Also used as railway ballast and in construction due to its extreme durability.
Geological facts
Blue quartzite is often mistaken for Blue Aventurine, but it lacks the 'aventurescence' (sparkling effect) caused by mica. It is one of the hardest and most chemically resistant rocks found on Earth's surface.
Field identification & locations
Identify by its ability to scratch glass and its grainy, sugary texture visible under a loupe. It will not react with acid (unlike marble). Commonly found in Brazil, India, and the Blue Ridge Mountains of the USA.
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