metamorphic
Quartzite
Quartzite (Silicon Dioxide, SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, white, or yellowish; Luster: Vitreous to waxy; Texture: Granular or sugary; Crystal structure: Trigonal (microcrystalline)
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, white, or yellowish
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, white, or yellowish; Luster: Vitreous to waxy; Texture: Granular or sugary; Crystal structure: Trigonal (microcrystalline)
Formation & geological history
Formed when quartz-rich sandstone is subjected to intense heat and pressure (metamorphism). Usually found in mountain belts and areas of ancient continental crust.
Uses & applications
Used predominantly in road construction, as railroad ballast, and for architectural stone. Higher purity samples are used for glassmaking and electronics.
Geological facts
Quartzite is so durable that it can withstand intense weathering; it often forms the caps of mountains and ridges because it resists erosion better than the rocks surrounding it.
Field identification & locations
Identified in the field by its extreme hardness (it will easily scratch glass) and its grainy, sandpaper-like appearance that does not rub off. Look for it in glacial till or riverbeds.
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