metamorphic
Quartzite Pebbles
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: White, gray, tan, and light blue-gray; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); High specific gravity (2.6-2.7).
- Hardness
- 7 on Mohs scale
- Color
- White, gray, tan, and light blue-gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White, gray, tan, and light blue-gray; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); High specific gravity (2.6-2.7).
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in convergent plate boundaries (mountain-building areas). These specific specimens have been rounded by water erosion in a fluvial or coastal environment.
Uses & applications
Used primarily in landscaping, water filtration, construction aggregate, and as decorative river stones. High-purity quartzite is also used for making glass and silicon metal.
Geological facts
Quartzite is so hard that it can scratch glass and steel. Most 'river rocks' found in gravel pits and garden centers are various forms of quartzite due to its extreme resistance to physical weathering.
Field identification & locations
Identify by its hardness (will scratch glass) and its sugary, granular surface texture when viewed closely. Common in old riverbeds, glacial moraines, and shorelines worldwide.
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