metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Gray, tan, or yellowish-white; Luster: Vitreous to dull; Structure: Granitoid/interlocking crystals; Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Gray, tan, or yellowish-white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray, tan, or yellowish-white; Luster: Vitreous to dull; Structure: Granitoid/interlocking crystals; Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Derived from the metamorphism of quartz sandstone through intense heat and pressure, typically during mountain-building events. Geological age varies by locality but can range from Precambrian to Cenozoic eras.
Uses & applications
Used extensively in road construction (crushed stone), as railway ballast, for floor tiles, and occasionally as decorative stone in architecture or landscaping.
Geological facts
Quartzite is so hard and durable that it often forms the crests of high ridges and mountains, as it resists erosion better than the surrounding softer rocks.
Field identification & locations
Identified in the field by its extreme hardness (cannot be scratched by a steel blade) and its tendency to break across the quartz grains rather than around them. Common in metamorphic belts globally.
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