sedimentary
Quartz Pebble
Crystalline Silica (SiO2)
Hardness: 7 (Mohs scale); Color: Tan/Cream/Light Brown; Luster: Dull to waxy; Crystal structure: Hexagonal (though not visible in this water-worn form); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Tan/Cream/Light Brown
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan/Cream/Light Brown; Luster: Dull to waxy; Crystal structure: Hexagonal (though not visible in this water-worn form); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed as quartz veins in metamorphic or igneous rocks, then weathered, broken off, and transported by water (rivers, streams, or oceans) over thousands of years to create its rounded, smooth shape.
Uses & applications
Commonly used in landscaping, as an abrasive, and in various construction materials; smaller polished versions are used for aquariums or decorative stone.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. These rounded pebbles are often called 'river stones' and have been smoothed by mechanical weathering in high-energy environments.
Field identification & locations
Identified in the field by its hardness (will scratch glass), lack of visible grains like sandstone, and smooth, rounded surface. Found in riverbeds and beaches worldwide.
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Sandstone or Siltstone
Arenite (if sandstone)
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Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
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Brown Sandstone (River Rock)
Arenite
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Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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