metamorphic
Quartzite
Silica (SiO2) quartzite
Hardness: 7 on Mohs scale; Color: Yellowish-tan/honey; Luster: Vitreous to dull; Crystal structure: Hexagonal (though interlocking grains in quartzite); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Yellowish-tan/honey
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: Yellowish-tan/honey; Luster: Vitreous to dull; Crystal structure: Hexagonal (though interlocking grains in quartzite); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure, causing the original quartz grains to recrystallize into a dense, interlocking matrix. Forms in convergent plate boundaries or orogenic belts.
Uses & applications
Used extensively in road construction gravel, as decorative landscaping stone, in the manufacture of glass, and occasionally as a building material due to its extreme durability.
Geological facts
Quartzite is so hard that it will scratch glass and even high-quality steel. It is often mistake for marble, but unlike marble which is made of calcite, quartzite will not react and bubble when exposed to acid.
Field identification & locations
Identify in the field by its hardness (scratches glass), grainy but non-porous texture, and lack of reaction to vinegar. Commonly found in mountainous regions or as river-worn pebbles in areas with metamorphic bedrock.
