metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: typically white to grey, but can be pink or reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: non-foliated, granular; Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to grey, but can be pink or reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: non-foliated, granular; Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, causing the original quartz grains to recrystallize into a dense interlocking mosaic. Found in orogenic belts worldwide.
Uses & applications
Used as a decorative stone in architecture (wall cladding, flooring), as railway ballast, crushed stone for road construction, and for manufacturing glass or industrial silica.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges because it resists weathering much better than surrounding rocks like shale or limestone.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and lack of foliation. Unlike marble, it will not fizz when exposed to weak acid. Often found in mountainous regions.
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