metamorphic
Blue Quartzite
Quartzite (primarily SiO2) with inclusions like Dumortierite or Crocidolite
Hardness: 7 on Mohs scale; Color: Blue-gray to dusty blue; Luster: Vitreous to waxy; Structure: Granular/Crystalline; Fracture: Conchoidal to irregular; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Blue-gray to dusty blue
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Blue-gray to dusty blue; Luster: Vitreous to waxy; Structure: Granular/Crystalline; Fracture: Conchoidal to irregular; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together. The blue coloration is often due to the presence of fibrous mineral inclusions like dumortierite.
Uses & applications
Used in landscaping, architectural stone, interior design (countertops), and as a gemstone for jewelry (cabochons and beads) or decorative carvings.
Geological facts
Quartzite is so durable that it often forms the caprock or ridges of mountain ranges because it resists weathering better than surrounding rocks. It can be distinguished from quartz by its internal grainy texture, which looks like fused sand grains.
Field identification & locations
Identify in the field by its extreme hardness (will scratch glass easily) and its sugary, granular appearance on fresh breaks. It is commonly found in ancient mountain belts in regions like Brazil, India, and the United States (Appalachians and Lake Superior region).
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