metamorphic
Quartzite
Quartzite
Hardness: 7 on Mohs scale; Color: white to light gray; Luster: vitreous to dull; Crystal structure: trigonal (microcrystalline); Cleavage: none; Specific gravity: 2.6 - 2.7
- Hardness
- 7 on Mohs scale
- Color
- white to light gray
- Luster
- vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: white to light gray; Luster: vitreous to dull; Crystal structure: trigonal (microcrystalline); Cleavage: none; Specific gravity: 2.6 - 2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the original quartz grains to recrystallize and fuse together. Typically Precambrian to Paleozoic in age.
Uses & applications
Used in construction as crushed stone for road gravel and railroad ballast, in glass manufacturing, and as a decorative stone for counter tops or wall cladding.
Geological facts
Quartzite is so tough that it often survives intense weathering that wears away surrounding softer rocks, leading to its prevalence in mountain summits and ridgelines. It will scratch glass easily.
Field identification & locations
Identify by its extreme hardness and grainy texture that resembles sandpaper but feels glassy. It can be found in mountain ranges worldwide where ancient sea beds were subducted. Collectors value unusual colors like pink or green caused by impurities.
