metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: white, grey, or yellowish with reddish iron stains; Luster: vitreous or dull; Structure: granoblastic; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- white, grey, or yellowish with reddish iron stains
- Luster
- vitreous or dull
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Physical properties
Hardness: 7 on Mohs scale; Color: white, grey, or yellowish with reddish iron stains; Luster: vitreous or dull; Structure: granoblastic; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz sandstone. Intense heat and pressure cause the quartz grains to recrystallize and fuse together, typically in orogenic belts of varying geological ages.
Uses & applications
Used as a decorative stone in construction, crushed stone for road aggregate, manufacturing of glass, and as a source of silica in metallurgy.
Geological facts
Quartzite is so strong that when it breaks, it breaks through the quartz grains rather than along the boundaries between them, unlike its parent rock sandstone.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Commonly found in mountainous regions or hilly outcrops where ancient crustal movements occurred.
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