metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white with brown spotting; Luster: Vitreous to dull; Structure: Granular, non-foliated; Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with brown spotting
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with brown spotting; Luster: Vitreous to dull; Structure: Granular, non-foliated; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure. This specific specimen shows signs of river or glacial tumbling, rounding its edges over thousands of years.
Uses & applications
Commonly used as crushed stone in road construction, as railway ballast, and in the production of glass and industrial ceramics.
Geological facts
Quartzite is so durable that it often remains as ridges or hills long after the surrounding softer rocks have eroded away. It is harder than steel and will easily scratch a glass plate.
Field identification & locations
Identify by its hardness (it cannot be scratched by a steel knife) and its grainy, crystalline texture that looks like sandpaper sugar but is smooth to the touch. Found in mountain ranges and riverbeds globally.
