metamorphic
Quartzite
Metamorphic rock (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan, often with iron staining; Luster: vitreous to dull; Crystal structure: granular/sugary; Cleavage: none.
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or tan, often with iron staining
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan, often with iron staining; Luster: vitreous to dull; Crystal structure: granular/sugary; Cleavage: none.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in orogenic belts. It originates from sedimentary environments like ancient beaches or dunes.
Uses & applications
Used in construction as road ballast, roofing granules, and dimension stone for flooring or countertops. High-purity quartzite is used to produce ferrosilicon and silicon metal.
Geological facts
Quartzite is so durable that it often forms the crests of mountain ridges because it resists erosion better than the surrounding rocks. It is distinct from sandstone because it fractures through the grains rather than around them.
Field identification & locations
Commonly found in riverbeds and glacial deposits. In the field, look for a very hard, non-porous rock that cannot be scratched by a steel knife and has a distinct crystalline, sugary texture on fresh breaks.
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