metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: white to light gray; Luster: vitreous to dull; Crystal structure: trigonal (granular); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- white to light gray
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: white to light gray; Luster: vitreous to dull; Crystal structure: trigonal (granular); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under intense heat and pressure, causing quartz grains to recrystallize and fuse together. Typically found in Precambrian or Paleozoic metamorphic belts.
Uses & applications
Used as a decorative stone in landscaping, a crushed stone in road construction, as ballast for railroads, and as a source of silica for glass and metal manufacturing.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks, forming prominent ridges or mountain peaks. It will scratch glass easily, unlike marble which it is often confused with.
Field identification & locations
Identify in the field by its hardness (scratches steel and glass) and its granular, sugary texture. It is extremely common worldwide in mountainous regions.
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