metamorphic
Quartzite
Quartzite (composed primarily of SiO2)
Hardness: 7 on Mohs scale; Color: tan, white, light gray, or brownish; Luster: vitreous to dull; Crystal structure: hexagonal (cryptocrystalline in texture); Cleavage: none, conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Color
- tan, white, light gray, or brownish
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, white, light gray, or brownish; Luster: vitreous to dull; Crystal structure: hexagonal (cryptocrystalline in texture); Cleavage: none, conchoidal fracture.
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure, typically during mountain-building events (orogeny).
Uses & applications
Used as a decorative stone, crushed stone for road construction, railroad ballast, and occasionally for kitchen countertops or floor tiles.
Geological facts
Quartzite is so hard that it will scratch glass and even high-grade steel. It is one of the most chemically and physically resistant rocks on the Earth's surface.
Field identification & locations
Identify by its hardness (cannot be scratched by a steel nail) and its granular, crystalline texture that breaks through the grains rather than around them. Common in folded mountain ranges.
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