metamorphic
Quartzite
Quartzite (SiO2 prominent)
Hardness: 7 on Mohs scale; Color: Brownish-red to tan; Luster: Dull to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Color
- Brownish-red to tan
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Brownish-red to tan; Luster: Dull to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during tectonic plate collisions and mountain-building events.
Uses & applications
Used in construction as crushed stone or decorative ballast, in the manufacture of glass, and occasionally as a semi-precious stone for lapidary work.
Geological facts
Quartzite is so tough that it often survives erosion better than the surrounding rocks, frequently forming the summits of hills and mountains.
Field identification & locations
Identify by its extreme hardness (it will easily scratch glass) and lack of visible grains compared to sandstone. Commonly found in riverbeds or mountain outcroppings.
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