metamorphic
Quartzite
Metamorphosed Quartz Sandstone (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: Tan to light brown; Luster: Vitreous to dull; Structure: Granoblastic (interlocking crystals); Cleavage: None, fractures conchoidally; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan to light brown
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to light brown; Luster: Vitreous to dull; Structure: Granoblastic (interlocking crystals); Cleavage: None, fractures conchoidally; Specific Gravity: 2.6-2.7
Formation & geological history
Formed when quartz-rich sandstone is subjected to intense heat and pressure (regional metamorphism), causing original quartz grains to recrystallize and fuse into a dense, hard rock.
Uses & applications
Used as crushed stone for road construction and railway ballast; as dimension stone for flooring, roofing, and wall cladding; and as a source of silica in glassmaking.
Geological facts
Quartzite is so tough that it often survives intense weathering better than other rocks, frequently capping mountain ridges. It is often confused with marble but can be distinguished by its much higher hardness.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its tendency to break across quartz grains rather than around them. It is globally abundant in metamorphic belts.
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