metamorphic
Quartzite
Metamorphosed Quartz Sandstone
Hardness (Mohs): 7; Color: White, gray, or tan; Luster: Vitreous to greasy; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Color
- White, gray, or tan
- Luster
- Vitreous to greasy
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Physical properties
Hardness (Mohs): 7; Color: White, gray, or tan; Luster: Vitreous to greasy; Crystal structure: Trigonal/Hexagonal; 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 cause quartz grains to recrystallize and fuse together, typically associated with convergent plate boundaries.
Uses & applications
Used in construction as road ballast, decorative stone in landscaping, and in the manufacturing of glass and ceramics due to its high silica content.
Geological facts
Quartzite is so durable that it can survive the intense mechanical weathering of rivers and glaciers better than almost any other rock. It is often harder than the steel of a masonry drill bit.
Field identification & locations
Identify in the field by its grainy appearance but smooth texture where grains have fused. It will scratch glass easily. Commonly found in folded mountain ranges and as stream pebbles.
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