metamorphic
Quartzite
Quartzite (primarily Silicon Dioxide, SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or yellowish as seen here; Luster: vitreous to grainy; Crystal structure: hexagonal (re-crystallized); Cleavage: none, breaks with a conchoidal or irregular fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or yellowish as seen here
- Luster
- vitreous to grainy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or yellowish as seen here; Luster: vitreous to grainy; Crystal structure: hexagonal (re-crystallized); Cleavage: none, breaks with a conchoidal or irregular fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed from quartz-rich sandstone subjected to extreme heat and pressure during regional metamorphism, leading to the interlocking of quartz grains. These are often found as water-worn river pebbles after erosion.
Uses & applications
Used as a decorative stone in landscaping, as a construction aggregate, in the production of glass, and occasionally for lapidary work or tumbled stones.
Geological facts
Quartzite is so hard that it will scratch glass and steel. It is much more durable than its parent rock, sandstone, and often forms resistant ridges in mountain ranges.
Field identification & locations
Identify by its extreme hardness and grainy, sugary appearance despite its smooth, water-worn exterior. It is commonly found in riverbeds, glacial deposits, and mountain outcrops. It feels denser and harder than similar-looking limestone or marble.
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