metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: gray, white, or tan with yellow/orange iron staining; Luster: vitreous to dull; Structure: non-foliated, granular; Cleavage: none.
- Hardness
- 7 (Mohs scale)
- Color
- gray, white, or tan with yellow/orange iron staining
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: gray, white, or tan with yellow/orange iron staining; Luster: vitreous to dull; Structure: non-foliated, granular; Cleavage: none.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in tectonic orogenic belts. This specific specimen shows water-worn rounding.
Uses & applications
Used widely in road construction, as railway ballast, for kitchen countertops, and as decorative stone in landscaping.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges because it weathers much more slowly than surrounding rocks.
Field identification & locations
Identify by its ability to scratch glass and its sugary, crystalline texture. It is extremely common in riverbeds and glacial deposits throughout North America and Europe.
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