metamorphic
Quartzite
Quartzite (composed primarily of Silica, SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, but pink or reddish if iron oxides are present; Luster: Vitreous (glassy); Crystal structure: Trigonal (microcrystalline); Cleavage: None, fractures conchoidally; Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, but pink or reddish if iron oxides are present; Luster: Vitreous (glassy); Crystal structure: Trigonal (microcrystalline); Cleavage: None, fractures conchoidally; Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the original quartz grains to recrystallize and fuse together into a dense, hard rock.
Uses & applications
Used in construction as crushed stone for road beds, in the glass industry, and as architectural stone for countertops and flooring. High-quality specimens are used for landscaping or carving.
Geological facts
Quartzite is so hard and durable that it often forms the tops of hills and ridges because it is highly resistant to chemical and physical weathering. It is harder than the steel of a knife blade.
Field identification & locations
Identify by its sugar-like texture on fresh surfaces (though it won't rub off) and its inability to be scratched by steel. Unlike marble, it does not fizz when in contact with acid. Commonly found in folded mountain belts.
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