metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Gray, white, or brown with possible iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular); Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Gray, white, or brown with possible iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray, white, or brown with possible iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular); Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together.
Uses & applications
Used in construction as crushed stone for road gravel, as decorative building stone, and historically as a raw material for stone tools (lithics) due to its conchoidal fracture pattern.
Geological facts
Quartzite is so durable that it often forms the crests of ridges and mountains because it resists weathering better than surrounding rocks. It is harder than steel and can easily scratch glass.
Field identification & locations
Identify by its 'sugary' texture and high hardness. Unlike sandstone, it will break through the quartz grains rather than around them. It is very common in ancient mountain belts.
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