metamorphic
Blue Quartzite (Aventurine)
Quartzite (primarily SiO2) with inclusions of Dumortierite or Magnesio-riebeckite
Hardness: 7 (Mohs scale); Color: Denim blue to grayish-blue; Luster: Vitreous to waxy; Crystal structure: Trigonal (granular); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Denim blue to grayish-blue
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Denim blue to grayish-blue; Luster: Vitreous to waxy; Crystal structure: Trigonal (granular); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Under intense heat and pressure, the sandstone recrystallizes. The blue color is typically the result of mineral inclusions like dumortierite that were integrated during the metamorphic process.
Uses & applications
Commonly used for decorative carvings, tumbled stones for crystal collections, jewelry (cabochons and beads), and occasionally as architectural stone for countertops or tiles.
Geological facts
While blue quartz can occur naturally, many polished specimens on the market are Blue Aventurine. It is often mistaken for Sodalite or Lapis Lazuli, but can be distinguished by its superior hardness and lack of white calcite or golden pyrite flecks.
Field identification & locations
Identify in the field by its grainy, sugary appearance when broken and its high hardness (it will easily scratch glass). Common locations include Brazil, India, and parts of the United States like Wisconsin or Virginia. For collectors, it is prized for its soothing color and durability.
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