metamorphic
Quartzite
Metamorphic Quartzite
Hardness: 7 on the Mohs scale. Color: Typically white, gray, or yellowish due to iron oxide staining. Luster: Vitreous to greasy. Crystal structure: Interlocking quartz crystals (non-foliated). Cleavage: None, breaks across grains (conchoidal fracture). 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: Typically white, gray, or yellowish due to iron oxide staining. Luster: Vitreous to greasy. Crystal structure: Interlocking quartz crystals (non-foliated). Cleavage: None, breaks across grains (conchoidal fracture). Specific gravity: 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or chert under high temperature and tectonic pressure. Geological age can range from Precambrian to Cenozoic.
Uses & applications
Used in construction, as crushed stone for roadbeds, in railway ballast, for dimension stone, and in the manufacturing of silica bricks and ferrosilicon.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why ridges formed of quartzite often persist as prominent mountain crests or hills.
Field identification & locations
Can be identified in the field by its hardness (will easily scratch glass and cannot be scratched by a steel knife) and the fact that it fractures across the quartz grains rather than around them, unlike sandstone. Found worldwide.
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