metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: white to light gray. Luster: vitreous to dull. Crystal structure: Trigonal (granular). Cleavage: none, conchoidal fracture. Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- white to light gray
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: white to light gray. Luster: vitreous to dull. Crystal structure: Trigonal (granular). Cleavage: none, conchoidal fracture. Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a decorative stone in architecture (countertops, flooring) or landscaping.
Geological facts
Quartzite is so hard that it can scratch steel. It is often confused with marble, but marble is much softer and reacts with acid, whereas quartzite does not.
Field identification & locations
Identify by its hardness (it will easily scratch glass) and lack of reaction to vinegar. Commonly found in folded mountain belts and ancient cratons worldwide.
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