metamorphic
Quartzite
Quartzite (composed primarily of SiO2)
Hardness: 7 on Mohs scale; Color: White to light grey; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- White to light grey
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to light grey; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional metamorphism of quartz sandstone under high heat and pressure, causing quartz grains to recrystallize and fuse into a dense rock.
Uses & applications
Used as decorative stone in architecture, as railway ballast, in the manufacture of glass and ceramics, and as a durable material for countertops and flooring.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than along their boundaries, unlike the sandstone from which it originated. Large deposits can be found in the Appalachian Mountains and the Brazilian Shield.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Often found in mountain ranges or areas of continental uplift. Look for a sugary texture on fresh breaks.
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