metamorphic
Quartzite
Quartzite (chiefly SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often with reddish/yellow iron staining; Luster: vitreous to dull; Structure: non-foliated granoblastic; Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often with reddish/yellow iron staining; Luster: vitreous to dull; Structure: non-foliated granoblastic; Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny). Earth's quartzite ranges from Proterozoic to Cenozoic in age.
Uses & applications
Used primarily in construction as road ballast, crushed stone, and building stone. High-purity quartzite is used to produce silica sand for glass making and metallurgy.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, frequently forming the peaks of mountains and ridges.
Field identification & locations
Identify by its extreme hardness (it will easily scratch glass) and its sugary, granular texture. Commonly found in folded mountain belts globally. It is often confused with marble but will not react with acid.
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