metamorphic
Quartzite
Quartzite (chiefly SiO2)
Hardness: 7 on Mohs scale; Color: Gray, white, or brownish; Luster: Vitreous to dull; Structure: Granoblastic (interlocking crystals); Cleavage: None; SG: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Gray, white, or brownish
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray, white, or brownish; Luster: Vitreous to dull; Structure: Granoblastic (interlocking crystals); Cleavage: None; SG: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny).
Uses & applications
Used as crushed stone for road construction, railroad ballast, and as a decorative stone in landscaping or interior design.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, forming prominent ridges and hills over millions of years.
Field identification & locations
Identified by its ability to scratch glass and its sugary, crystalline texture. It is found globally in ancient mountain belts such as the Appalachians or the Alps.
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