metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically pinkish-brown, grey, or white; Luster: vitreous (glassy) to dull; Crystal structure: trigonal (granular); Cleavage: none; Specific gravity: approx. 2.6
- Hardness
- 7 on Mohs scale
- Color
- typically pinkish-brown, grey, or white
- Luster
- vitreous (glassy) to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically pinkish-brown, grey, or white; Luster: vitreous (glassy) to dull; Crystal structure: trigonal (granular); Cleavage: none; Specific gravity: approx. 2.6
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. Geological ages vary widely from Precambrian to Cenozoic.
Uses & applications
Used in construction as crushed stone for road ballast, as a decorative building stone (facades), and sometimes in glass manufacturing if high purity.
Geological facts
Quartzite is so tough that it often outlasts surrounding rocks through erosion, forming the caps of many prominent ridges and peaks. It is harder than steel and will scratch a glass plate.
Field identification & locations
Identify by its ability to scratch glass and lack of reaction to acid. In the field, look for a sugary or granular appearance where individual sand grains have fused together. Common in ancient mountain belts.
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