metamorphic
Quartzite
Metamorphosed Sandstone (Mainly SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often tan or yellow due to impurities; Luster: vitreous to waxy; Structure: granular, non-foliated crystalline; Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often tan or yellow due to impurities; Luster: vitreous to waxy; Structure: granular, non-foliated crystalline; Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under extreme heat and pressure, typically during mountain-building events (orogeny). Its geological age can range from Precambrian to Cenozoic depending on the source rock location.
Uses & applications
Used extensively in construction as road ballast, railway ballast, and decorative stone. High-purity quartzite is used to produce silica sand for glassmaking and silicon metal.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caps of ridges and mountains because it weathers much more slowly than surrounding rocks.
Field identification & locations
Identify in the field by its ability to scratch glass and its grainy, sandpaper-like texture that lacks the visible pores of sandstone. It is commonly found in metamorphic terranes worldwide.
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