metamorphic
Quartzite Pebble (River Rock)
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: White, cream, or off-white with tan/iron staining; Luster: Vitreous to waxy (when wet); Crystal structure: Hexagonal/Trigonal system (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.65
- Hardness
- 7 (Mohs scale)
- Color
- White, cream, or off-white with tan/iron staining
- Luster
- Vitreous to waxy (when wet)
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Physical properties
Hardness: 7 (Mohs scale); Color: White, cream, or off-white with tan/iron staining; Luster: Vitreous to waxy (when wet); Crystal structure: Hexagonal/Trigonal system (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure Recrystallize the sand grains into a dense, interlocking matrix. This specimen shows water-worn rounding, likely from a fluvial (river) or glacial environment during the Quaternary period.
Uses & applications
Used widely as decorative landscaping stone, in road construction, and as a component in glass manufacturing. Smooth specimens are often used for stone massage or in aquarium hobbyist displays.
Geological facts
Quartzite is so tough that unlike sandstone, which breaks around its grains, quartzite breaks straight through the grains. It is often resistant to chemical weathering, causing it to form many of the ridges and peaks in mountain ranges.
Field identification & locations
Identify by its hardness (it will easily scratch glass) and lack of Fizzing when in contact with acid (unlike marble). Common in riverbeds and glacial tills. Look for the 'sugary' texture visible on fresh breaks beneath the smooth water-worn surface.
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