metamorphic
Quartzite
Metamorphosed Quartz Sandstone
Hardness: 7 on Mohs scale; Color: Reddish-pink to tan due to iron oxides; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 to 2.7.
- Hardness
- 7 on Mohs scale
- Color
- Reddish-pink to tan due to iron oxides
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-pink to tan due to iron oxides; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 to 2.7.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together, creating a much harder rock. This specific specimen shows iron staining and weathering common in stream-bed or glacial environments.
Uses & applications
Used frequently in construction as road ballast, gravel, and dimension stone. Highly valued in high-quality specimens for landscaping, flooring, and occasionally as a semi-precious stone for ornamental carvings or cabochons.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges it was formed in, becoming the main component of resistant ridges and hilltops. Unlike sandstone, when quartzite breaks, it fractures through the quartz grains rather than around them.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass or steel) and sugary, granular texture. It is found globally, particularly in areas of ancient tectonic activity such as the Appalachian or Great Lakes regions of North America.
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