metamorphic
Blue Quartzite (Aventurine variety)
Silicon Dioxide (SiO2) with inclusions of Dumortierite or Magnesio-riebeckite
Hardness: 7 on Mohs scale; Color: Denim blue to grayish-blue; Luster: Vitreous to waxy; Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.63 - 2.65
- Hardness
- 7 on Mohs scale
- Color
- Denim blue to grayish-blue
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Denim blue to grayish-blue; Luster: Vitreous to waxy; Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.63 - 2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, trapping blue mineral inclusions (like dumortierite) that provide the color.
Uses & applications
Used primarily for ornamental purposes, jewelry (beads and cabochons), landscaping stones, and as a decorative building material due to its extreme durability and weather resistance.
Geological facts
Unlike many blue minerals that are dyed, natural blue quartzite gets its color from microscopic mineral inclusions. It is one of the hardest and most chemically resistant rocks frequently found in the Earth's crust.
Field identification & locations
Identify in the field by its grainy, sugary texture when broken and its inability to be scratched by a steel knife. Common locations include Brazil, India, South Africa, and parts of the United States (like Arizona and Wisconsin).
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