metamorphic
Blue Quartzite
Quartzite (primarily SiO2) with inclusions like Dumortierite or Magnesio-riebeckite
Hardness: 7 (Mohs scale); Color: Grayish-blue to deep blue with rust-colored iron staining; Luster: Vitreous to dull; Crystal structure: Hexagonal/Trigonal (granular); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Grayish-blue to deep blue with rust-colored iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Grayish-blue to deep blue with rust-colored iron staining; Luster: Vitreous to dull; Crystal structure: Hexagonal/Trigonal (granular); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure Recrystallize the quartz grains into a dense, interlocking matrix. The blue tint is usually caused by microscopic inclusions of fibrous minerals.
Uses & applications
Used for decorative landscaping, architectural stone, river rock in garden design, and occasionally as an ornamental gemstone for lapidary work (cabs or tumbling).
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than around them. Blue varieties are much rarer than the common white or pink versions and are often used by collectors for their unique hue.
Field identification & locations
Identify by its ability to scratch glass and its granular, sugary texture. It is commonly found in ancient mountain belts and riverbeds in regions like the Blue Ridge Mountains (USA) or parts of Brazil and South Africa.
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