metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often pink or reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: Trigonal (hexagonal) crystalline structure; Cleavage: None, breaks with a conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often pink or reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: Trigonal (hexagonal) crystalline structure; Cleavage: None, breaks with a conchoidal fracture.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together into a dense, hard rock. Typical geological ages range from Precambrian to Mesozoic.
Uses & applications
Used primarily in building construction as a decorative stone, crushed stone for road aggregate, and historically for making tools. High-purity quartzite is used to produce glass and ferrosilicon.
Geological facts
Quartzite is so tough that it often survives erosion better than other rocks, frequently capping hills or ridges. It is often confused with marble, but quartzite is much harder and will not react with acid.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel nail) and the way it breaks through the grain rather than around it. Commonly found in mountain ranges and plateaus worldwide.
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