metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or pink (here showing reddish hues due to iron oxides); Luster: Vitreous/glassy to waxy; Structure: Granular/crystalline; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous/glassy to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or pink (here showing reddish hues due to iron oxides); Luster: Vitreous/glassy to waxy; Structure: Granular/crystalline; Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure reciprocal to tectonic compression cause quartz grains to recrystallize and fuse together, typically during orogenic (mountain-building) events.
Uses & applications
Used in construction as crushed stone for road ballast, as a dimension stone for flooring and countertops, and in glass manufacturing if the silica content is high enough.
Geological facts
Quartzite is so tough that it often breaks through the quartz grains rather than along their boundaries, unlike sandstone. It is highly resistant to chemical weathering.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and the way it breaks into sharp, conchoidal fragments. Common in ancient mountain belts and glacial till.
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