metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan (reddish-pink in this specimen due to iron oxide); Luster: vitreous to dull; Texture: granoblastic with a sugary appearance; Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan (reddish-pink in this specimen due to iron oxide); Luster: vitreous to dull; Texture: granoblastic with a sugary appearance; Cleavage: none (conchoidal fracture).
Formation & geological history
Formed from the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together, eliminating pore space. It can range from Precambrian to Cenozoic in age.
Uses & applications
Used extensively in construction as crushed stone for roadbeds and railway ballast, as a dimension stone for flooring and countertops, and historically as a material for stone tools.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the resistant caps of ridges and mountains. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its extreme hardness and the fact that it breaks across the quartz grains rather than around them (unlike sandstone). Found globally in mountainous regions and ancient shields.
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