sedimentary
Quartz Pebble (Chert / Chalcedony)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: brownish-pink to tan with translucent microcrystalline regions; Luster: waxy to vitreous; Crystal system: Trigonal/Microcrystalline; Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Luster
- waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: brownish-pink to tan with translucent microcrystalline regions; Luster: waxy to vitreous; Crystal system: Trigonal/Microcrystalline; Specific gravity: 2.65
Formation & geological history
Formed through the precipitation of silica-rich fluids in sedimentary rock cavities or during diagenesis, subsequently weathered and rounded into a pebble by stream or beach action.
Uses & applications
Commonly collected as river stones, used in landscaping, rock tumbling, ornamental crafts, and historically for flintknapping.
Geological facts
Water-worn quartz and chert pebbles are among the most durable rocks on Earth, surviving millions of years of erosion that wears away softer surrounding minerals.
Field identification & locations
Identified by its hardness (scratches glass), waxy or greasy luster, shell-like (conchoidal) fracture, and smooth rounded pebble shape. Found globally in riverbeds, glacial deposits, and beaches.
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