metamorphic
Quartzite
Quartzite (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: typically white to grey, with iron staining (yellow/orange); Luster: vitreous to waxy; Texture: sugary to smooth when water-worn; Cleavage: none; Fracture: conchoidal or irregular.
- Hardness
- 7 on Mohs scale
- Color
- typically white to grey, with iron staining (yellow/orange)
- Luster
- vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to grey, with iron staining (yellow/orange); Luster: vitreous to waxy; Texture: sugary to smooth when water-worn; Cleavage: none; Fracture: conchoidal or irregular.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under high heat and pressure, where quartz grains recrystallize and fuse together. These are often Proterozoic to Paleozoic in age when found as larger formations.
Uses & applications
Used in construction as road ballast, decorative garden stone, as a source for silica in glassmaking, and in high-quality slabs for countertops.
Geological facts
Quartzite is so hard and durable that it often remains as ridges or peaks while softer surrounding rock erodes away. It can be distinguished from sandstone because it breaks across the quartz grains rather than around them.
Field identification & locations
Identify in the field by its inability to be scratched by a steel blade and its granular, crystalline appearance. Commonly found in riverbeds as rounded cobbles or in metamorphic mountain belts worldwide.
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