metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: tan, gray, or white with sugary texture; Luster: vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- tan, gray, or white with sugary texture
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, gray, or white with sugary texture; Luster: vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure from tectonic activity. Most specimens date back millions to billions of years.
Uses & applications
Used in construction as crushed stone or road ballast, as dimension stone for wall coverings and flooring, and occasionally as a source of silica in glass manufacturing.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges it was part of, forming resistant ridges after other rocks have eroded away. It is harder than steel.
Field identification & locations
Identify by its ability to scratch glass and its granular, sugary appearance that looks like compressed sand grains. Common in mountainous regions with a history of continental collisions.
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