metamorphic
Quartzite
Quartzite (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: Reddish-pink, purple-brown; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-pink, purple-brown
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-pink, purple-brown; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during mountain-building events (orogeny). The red hue is due to iron oxide impurities.
Uses & applications
Used in construction as road ballast, railway ballast, and decorative stone. Sometimes used in jewelry or as tumbled stones for collectors.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caprock or spine of mountain ranges. It is harder than the sandstone it originates from and will typically break through quartz grains rather than around them.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and sandy, sugary texture on fresh breaks. Found globally, prominent in the Appalachian Mountains, Lake Superior region, and Brazil. Collectors look for unique colors or banded patterns.
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