sedimentary
Quartz Pebble (Chalcedony / Agate)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Grayish-brown with translucent chalcedony patterns; Luster: Waxy to vitreous when wet; Structure: Cryptocrystalline/Microcrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Grayish-brown with translucent chalcedony patterns
- Luster
- Waxy to vitreous when wet
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Grayish-brown with translucent chalcedony patterns; Luster: Waxy to vitreous when wet; Structure: Cryptocrystalline/Microcrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from silica-rich fluid precipitation in rock cavities, later eroded, water-worn, and rounded by stream or ocean wave action over thousands to millions of years.
Uses & applications
Used primarily for lapidary arts, rock tumbling, decorative landscaping, and beach pebble collecting.
Geological facts
Water-rounded pebbles like this are natural lapidary specimens smoothed entirely by hydrodynamic action without artificial polishing machinery.
Field identification & locations
Identified by its high hardness (scratches glass), waxy luster, smooth water-worn surface, and partial translucency. Widely found on coastal beaches, riverbeds, and gravel bars.
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