metamorphic
Quartzite Pebble
Metamorphic Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: White, grey, reddish-brown (from iron oxidation); Luster: Vitreous to dull; Crystal structure: Trigonal (granular); Cleavage: None; Specific gravity: ~2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- White, grey, reddish-brown (from iron oxidation)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: White, grey, reddish-brown (from iron oxidation); Luster: Vitreous to dull; Crystal structure: Trigonal (granular); Cleavage: None; Specific gravity: ~2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone. Intense heat and pressure cause quartz grains to recrystallize and fuse together. This pebble has been subsequently water-worn and smoothed by river or glacial transport.
Uses & applications
Used as a decorative gravel, in landscaping, as a construction aggregate, and occasionally in the production of glass or silicone.
Geological facts
Quartzite is so tough that it often outlasts the surrounding softer rocks, eventually forming high ridges or resistant pebbles found far from their original source. Unlike sandstone, quartzite fractures across the sand grains rather than around them.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and granular texture. Commonly found in riverbeds, till deposits, and mountain ranges. Collectors look for unique banding or color patterns.
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