metamorphic
Quartzite
Metamorphic Rock (Quartzite)
Hardness: 7 on Mohs scale. Color: White to grey/brown due to impurities. Luster: Vitreous to dull. Crystal structure: Granular, interlocking quartz grains. Cleavage: Indistinct. Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- White to grey/brown due to impurities
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: White to grey/brown due to impurities. Luster: Vitreous to dull. Crystal structure: Granular, interlocking quartz grains. Cleavage: Indistinct. Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure causes recrystallization of the quartz grains, making it extremely durable. It can date back from any geological era, often Proterozoic.
Uses & applications
Used as crushed stone for road construction, railway ballast, and in some decorative stone applications. High-purity quartzite is a source of silica for glass and silicon metal production.
Geological facts
Quartzite is so tough that it often forms the tops of hills and ridges because it resists weather and erosion better than the surrounding rock.
Field identification & locations
Identify by its hardness (scratches glass) and granular texture. Unlike marble, it will not fizz when exposed to acid. Commonly found in mountainous regions or ancient shields.
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