metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray but can be pink or reddish; Luster: vitreous (glassy) to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: approx. 2.6
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray but can be pink or reddish
- Luster
- vitreous (glassy) to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray but can be pink or reddish; Luster: vitreous (glassy) to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: approx. 2.6
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together into a dense, solid rock structure. Most deposits vary in age from Precambrian to more recent tectonic events.
Uses & applications
Used in construction as crushed stone for road beds and railway ballast, as dimension stone for counter tops and flooring, and occasionally in glassmaking if pure enough.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, mountain builders frequently find it forming the caps of ridges because it is so resistant to chemical and physical weathering.
Field identification & locations
Identify in the field by its grainy, sugary texture and extreme hardness (it will easily scratch glass). Unlike sandstone, it will break across the grains rather than around them. Found globally in mountainous regions.
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