metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: Generally white to grey, but can be stained brown, yellow, or pink by iron oxides. Luster: Vitreous to greasy. Crystal structure: Trigonal (microcrystalline interlocking quartz grains). Cleavage: None (fractures conchoidally). 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 white to grey, but can be stained brown, yellow, or pink by iron oxides. Luster: Vitreous to greasy. Crystal structure: Trigonal (microcrystalline interlocking quartz grains). Cleavage: None (fractures conchoidally). Specific gravity: 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert under high temperature and pressure during regional metamorphism. Geological age varies widely depending on the formation site, ranging from Precambrian to Cenozoic.
Uses & applications
Used in construction, as crushed stone for road bases, in the manufacturing of refractory bricks, metallurgical silica, and occasionally as a decorative dimension stone or in countertops.
Geological facts
Unlike sandstone, which breaks around the individual sand grains, quartzite breaks straight through the grains because the quartz crystals are thoroughly welded together by silica cement.
Field identification & locations
Extremely resistant to weathering and erosion, often forming prominent ridges and hills. Found worldwide in mountain belts and ancient cratons.
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