metamorphic
Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or brown/yellow due to iron oxides; Luster: Vitreous to dull; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None/Conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or brown/yellow due to iron oxides
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or brown/yellow due to iron oxides; Luster: Vitreous to dull; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None/Conchoidal fracture.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, usually at convergent plate boundaries. The sand grains recrystallize and fuse together.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a decorative stone in landscaping or architectural cladding.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks; when broken, it fractures through the sand grains rather than around them, which distinguishes it from sandstone.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Often found in riverbeds as rounded cobbles like this specimen, smoothed by water erosion.
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