metamorphic
Quartzite
Quartzite (SiO2 main component)
Hardness: 7 on Mohs scale; Color: light gray, white, or tan; Luster: vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: Indistinct; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- light gray, white, or tan
- Luster
- vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: light gray, white, or tan; Luster: vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: Indistinct; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, causing the original quartz grains to recrystallize into an interlocking mosaic.
Uses & applications
Used as crushed stone for road construction, railroad ballast, and as a raw material in the glass and ceramic industries. Higher grade pieces are used for countertops and floor tiles.
Geological facts
Quartzite is so hard that it can scratch glass and steel. It is often confused with marble, but can be distinguished by its superior hardness and lack of reaction to acid.
Field identification & locations
Identify by its sugary, granular surface and extreme hardness. It won't be scratched by a knife. Commonly found in folded mountain belts and ancient cratons globally.
