mineral
Quartz (Gravel Pebble)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: off-white/grey; Luster: Vitreous to dull; Crystal structure: Trigonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- off-white/grey
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: off-white/grey; Luster: Vitreous to dull; Crystal structure: Trigonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65
Formation & geological history
Formed from cooling magma or precipitation in hydrothermal veins; this specific piece has been weathered and rounded as alluvial gravel in a stream or river bed.
Uses & applications
Used in glassmaking, electronics (piezoelectric properties), abrasives, and as construction aggregate. Small pebbles are often used in landscaping.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. It is extremely resistant to physical and chemical weathering, which is why it often remains as small pebbles while other minerals dissolve.
Field identification & locations
Identify by its hardness (it will scratch glass) and lack of cleavage. Commonly found in gardens, driveways, riverbeds, and beaches worldwide.
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Nephrite
Mineral/Rock
Banded Gneiss (River Rock/Pebble)
Gneiss (specifically a banded variety often found as a river rock)
Metamorphic Rock
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Biotite Schist
Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]
metamorphic