metamorphic
Quartzite
Quartzite
Hardness: 7 on the Mohs scale. Color: Generally white to gray, but can be pink, yellow, or brown due to iron oxide impurities. Luster: Vitreous to greasy. Crystal structure: Interlocking quartz crystals. Cleavage: None (fractures conchoidally). Specific gravity: 2.65.
- Hardness
- 7 on the Mohs scale
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on the Mohs scale. Color: Generally white to gray, but can be pink, yellow, or brown due to iron oxide impurities. Luster: Vitreous to greasy. Crystal structure: Interlocking quartz crystals. Cleavage: None (fractures conchoidally). Specific gravity: 2.65.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, typically through tectonic compression during mountain-building events (regional metamorphism). Geological age varies widely depending on the formation site, ranging from Precambrian to Cenozoic eras.
Uses & applications
Used as crushed stone in road construction, railroad ballast, roofing granules, and as a decorative stone or countertop material in interior design.
Geological facts
Because quartz is extremely resistant to weathering, quartzite ridges often stand out as prominent hills or mountain crests in the landscape. Unlike sandstone, quartzite breaks across the grains rather than around them when fractured.
Field identification & locations
Can be identified by its sugary texture on broken surfaces and its extreme hardness, which allows it to scratch glass easily. Commonly found in mountainous regions and old orogenic belts worldwide.
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