metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: White to light grey; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Specific gravity: 2.6-2.7. Very durable and resistant to scratching.
- Hardness
- 7 (Mohs scale)
- Color
- White to light grey
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 (Mohs scale); Color: White to light grey; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Specific gravity: 2.6-2.7. Very durable and resistant to scratching.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone subjected to high heat and pressure, causing the original quartz grains to recrystallize into an interlocking mosaic.
Uses & applications
Used in construction for road ballast, floor coverings, and wall surfacing. High-purity quartzite is used to produce silica sand for glassmaking and silicon for industrial applications.
Geological facts
Quartzite is so tough that it often survives intense weathering and erosion better than surrounding rocks, frequently forming the tops of ridges and hills. It is often confused with marble but can be distinguished by its superior hardness.
Field identification & locations
Identify in the field by its grainy, sugary texture and extreme hardness (it will easily scratch glass). Commonly found in folded mountain belts and ancient shield areas. Tumbled river stones like this one are ubiquitous worldwide.
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