metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: white, grey, or yellowish. Luster: vitreous to dull. Crystal Structure: trigonal (granular). Cleavage: none. Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- white, grey, or yellowish
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: white, grey, or yellowish. Luster: vitreous to dull. Crystal Structure: trigonal (granular). Cleavage: none. Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under high heat and pressure. This usually occurs during mountain-building events (orogenic processes).
Uses & applications
Used in construction as road ballast, roofing tiles, and decorative stone. Highly valued in high-purity form for glass making and silicon production.
Geological facts
Quartzite is so durable that it often survives intense weathering better than the rocks surrounding it, forming the caps of many mountain ridges.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. It is commonly found in fold mountain belts globally. Collectors look for sugary textures.
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