metamorphic
Quartzite
Metamorphosed Quartz Sandstone
Hardness: 7 on Mohs scale. Color: Generally yellowish-brown, tan, or white due to iron oxide impurities. Luster: Vitreous to greasy. Crystal structure: Non-foliated, interlocking quartz grains. Cleavage: None (fractures across grains). Specific gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on Mohs scale. Color: Generally yellowish-brown, tan, or white due to iron oxide impurities. Luster: Vitreous to greasy. Crystal structure: Non-foliated, interlocking quartz grains. Cleavage: None (fractures across grains). Specific gravity: 2.65.
Formation & geological history
Formed from quartz-rich sandstone subjected to high heat and pressure during tectonic processes, typically in mountain-building events over millions of years.
Uses & applications
Used in construction, as road aggregate, railroad ballast, manufacturing of silica brick, and sometimes as decorative stone or countertops.
Geological facts
Unlike sandstone which breaks around the grains, quartzite breaks straight through the quartz grains because of the extreme bonding pressure it underwent during formation.
Field identification & locations
Extremely durable and weather-resistant, commonly found in mountainous regions and ancient cratons worldwide. Identified by its hardness and inability to be scratched by a steel knife.
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