metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: white, gray, or pinkish; Luster: vitreous to dull; Crystal structure: hexagonal (granular/crystalline texture); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- white, gray, or pinkish
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: white, gray, or pinkish; Luster: vitreous to dull; Crystal structure: hexagonal (granular/crystalline texture); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure, causing quartz grains to recrystallize into a hard, interlacing network. Most date back to the Proterozoic or Paleozoic eras.
Uses & applications
Used widely in road construction (aggregate), as a decorative building stone, in high-end countertops, and as a source of silica for glass manufacturing.
Geological facts
Quartzite is so hard that it will scratch glass and steel. In prehistoric times, it was occasionally used as a substitute for flint to create stone tools, though it is more difficult to flake.
Field identification & locations
Identify by its ability to scratch glass and its granular, sugary appearance when broken. Unlike marble, it does not react to acid. Commonly found in folded mountain belts globally.
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