metamorphic
Blue Quartz (specifically Dumortierite Quartz)
Silicon Dioxide (SiO2) with inclusions of Dumortierite (Al7BO3(SiO4)3O3)
Hardness: 7 (Mohs scale); Color: Denim blue to grayish-blue with white streaks; Luster: Vitreous to waxy; Crystal structure: Hexagonal (trigonal) system for quartz; Cleavage: None/Conchoidal fracture; Specific gravity: approx. 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- Denim blue to grayish-blue with white streaks
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Denim blue to grayish-blue with white streaks; Luster: Vitreous to waxy; Crystal structure: Hexagonal (trigonal) system for quartz; Cleavage: None/Conchoidal fracture; Specific gravity: approx. 2.65.
Formation & geological history
Formed through regional metamorphism where quartz-rich rocks are subjected to high pressure and heat, allowing aluminum-rich dumortierite inclusions to grow within the quartz matrix. Most deposits range from Proterozoic to Cenozoic eras.
Uses & applications
Primarily used as an ornamental stone, for lapidary work (beads, cabochons, carvings), and as a gemstone for collectors and metaphysical practitioners.
Geological facts
Unlike 'Blue Lace Agate' which is banded, Blue Quartz gets its color from tiny fibrous mineral inclusions of Dumortierite. It is often mistaken for Sodalite or Lapis Lazuli, but is significantly harder.
Field identification & locations
Identify in the field by its superior hardness (it will scratch glass and steel) and its characteristic grainy, denim-blue appearance. Common locations include Brazil, South Africa, and Madagascar.
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