metamorphic
Quartzite
Metamorphosed Quartz Sandstone
Hardness: 7 on the Mohs scale; Color: typically white, gray, or tan; Luster: vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: none (breaks with conchoidal fracture).
- Hardness
- 7 on the Mohs scale
- Color
- typically white, gray, or tan
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on the Mohs scale; Color: typically white, gray, or tan; Luster: vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: none (breaks with conchoidal fracture).
Formation & geological history
Formed through the heating and pressure (metamorphism) of quartz-rich sandstone. It originates in mountain-building environments where tectonic plates converge, effectively fusing sandstone grains together.
Uses & applications
Used in construction as crushed stone for road ballast, as a decorative building stone, and in some industrial glass-making processes because of its high silica content.
Geological facts
Quartzite is so tough that it often resists weathering better than surrounding rocks, frequently forming the peaks of mountains or ridges.
Field identification & locations
Identify in the field by its hardness (it will easily scratch glass) and its sugary, crystalline appearance on fresh surfaces. Unlike marble, it does not fizz when in contact with acid.
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