metamorphic
Red Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: reddish-pink due to iron oxide impurities; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Specific gravity: 2.6-2.7. It is extremely tough and breaks across grains rather than around them.
- Hardness
- 7 on Mohs scale
- Color
- reddish-pink due to iron oxide impurities
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: reddish-pink due to iron oxide impurities; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Specific gravity: 2.6-2.7. It is extremely tough and breaks across grains rather than around them.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the parent quartz grains to recrystallize and fuse together into a dense, crystalline rock.
Uses & applications
Used as decorative stone, crushed stone for road construction, railroad ballast, and occasionally in jewelry as a cabochon or tumbled stone.
Geological facts
Quartzite is so durable that it often remains as ridges or peaks while softer rocks around it erode away. It is often confused with marble, but quartzite is much harder and will not react with acid.
Field identification & locations
Identified in the field by its sugary, crystalline surface and its inability to be scratched by a steel knife. Common in ancient mountain belts and shield areas like the Canadian Shield or the Appalachians.
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