metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: tan, yellow-brown, greyish to off-white; Luster: vitreous to dull/waxy; Structure: non-foliated granoblastic network of interlocked quartz grains; Cleavage: none; Specific Gravity: approx 2.65.
- Hardness
- 7 on Mohs scale
- Color
- tan, yellow-brown, greyish to off-white
- Luster
- vitreous to dull/waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, yellow-brown, greyish to off-white; Luster: vitreous to dull/waxy; Structure: non-foliated granoblastic network of interlocked quartz grains; Cleavage: none; Specific Gravity: approx 2.65.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone under high pressure and temperature, causing individual quartz grains to recrystallize and tightly interlock.
Uses & applications
Used in construction as crushed stone, road ballast, decorative garden stone, and historically as a tough material for stone tools.
Geological facts
Because quartzite recrystallizes completely, when it breaks, it fractures directly through the quartz grains rather than around them, unlike its precursor sandstone.
Field identification & locations
Identified in the field by its extreme hardness (scratches glass easily), sugary to smooth texture, and inability to be scratched by a steel knife blade. Widely abundant globally in mountainous terrain and river beds.
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