metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often with pink or peach tones due to iron oxides; Luster: vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: none, breaks with a conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often with pink or peach tones due to iron oxides; Luster: vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: none, breaks with a conchoidal fracture.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together. This specimen appears to be a water-worn, rounded river cobble.
Uses & applications
Used as a decorative stone in landscaping, as a building material, and in road construction as crushed stone. Also popular as a lapidary material for tumbling.
Geological facts
Quartzite is so tough that it often survives intense weathering and transport in rivers longer than other rock types. It is often confused with marble, but quartzite is much harder and will not react with acid.
Field identification & locations
Identify by its hardness (it will scratch glass) and its granular, sugary appearance when freshly broken. Commonly found in mountain belts and riverbeds eroding from metamorphic terrains.
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