metamorphic
Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs); Color: Tan, beige, or yellowish-brown; Luster: Dull to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs)
- Color
- Tan, beige, or yellowish-brown
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 (Mohs); Color: Tan, beige, or yellowish-brown; Luster: Dull to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed when quartz-rich sandstone is subjected to heat, pressure, and chemical activity of metamorphism. This specimen shows significant rounding due to fluvial (river) or glacial transport.
Uses & applications
Commonly used in construction as crushed stone for road gravel, railroad ballast, and in the production of glass and industrial ceramics.
Geological facts
Quartzite is one of the most durable and resistant rocks on Earth's surface. It is often harder than the steel of a pocket knife. Famous landscapes like the Devil's Lake in Wisconsin are composed of massive quartzite formations.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a steel nail) and its grainy, sandpaper-like texture that doesn't rub off. Commonly found in riverbeds, glacial tills, and ancient mountain ranges.
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