metamorphic
Quartzite River Pebble
Metamorphic Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white with tan and dark inclusions; Luster: Vitreous to waxy when wet, dull when dry; Crystal Structure: Granular/Microcrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with tan and dark inclusions
- Luster
- Vitreous to waxy when wet, dull when dry
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with tan and dark inclusions; Luster: Vitreous to waxy when wet, dull when dry; Crystal Structure: Granular/Microcrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, causing sand grains to recrystallize into a dense network. This specimen has been rounded by fluvial (river) erosion over thousands of years.
Uses & applications
Used as decorative landscaping stone, drainage material, and sometimes crushed for high-silica industrial applications. Smooth pebbles are popular for 'rock painting' and meditation gardens.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges it formed in, eventually ending up as rounded pebbles in riverbeds far from its source. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify by its hardness (cannot be scratched by a knife) and its grainy, 'sugary' texture visible under a lens. It lack the bubbles of igneous rocks and the layers of shale. Common in riverbeds globally.
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