metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, brown, or reddish-orange due to iron oxidation; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Specific gravity: 2.6 - 2.7.
- Hardness
- 7 (Mohs scale)
- Color
- Tan, brown, or reddish-orange due to iron oxidation
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, brown, or reddish-orange due to iron oxidation; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Specific gravity: 2.6 - 2.7.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, causing recrystallization. This specific specimen has been further smoothed and rounded by long-term water erosion in a river or beach environment.
Uses & applications
Large deposits are used in road construction, railway ballast, and the production of glass or silica-based ceramics. As a pebble, it is often used for decorative landscaping or as a tumbling stone for hobbyists.
Geological facts
Quartzite is so hard it will scratch glass and steel. It is more resistant to weathering than the sandstone from which it originated, often forming ridges or resistant outcrops in mountainous regions.
Field identification & locations
Identify by its extreme hardness and the fact that it breaks across the sand grains rather than around them. Found in riverbeds, glacial tills, and ancient sedimentary basins worldwide.
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