metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan to reddish-brown; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63-2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan to reddish-brown
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to reddish-brown; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63-2.65
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure, causing the quartz grains to recrystallize and fuse into a solid mass. Likely from the Proterozoic or Paleozoic era.
Uses & applications
Used in construction as road ballast, railway ballast, and dimension stone; also used in the glass and chemical industries for high-silica content.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, often forming the caps of ridges and mountains. It is harder than a steel knife and will scratch glass easily.
Field identification & locations
Identify by its extreme hardness and grainy, sugary texture on fresh breaks. It is commonly found in riverbeds, glacial deposits, and mountain ranges where tectonic activity has occurred.
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