metamorphic
Beach Pebble Quartzite / Chalcedony Pebble
Silicon Dioxide (SiO2)
Hardness: 6.5-7 Mohs. Color: Grayish-green to translucent blue-gray with thin quartz mineral veins. Luster: Vitreous to waxy (smoothly water-worn). Crystal Structure: Microcrystalline to trigonal. Cleavage: None, conchoidal fracture.
- Hardness
- 6
- Luster
- Vitreous to waxy (smoothly water-worn)
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Physical properties
Hardness: 6.5-7 Mohs. Color: Grayish-green to translucent blue-gray with thin quartz mineral veins. Luster: Vitreous to waxy (smoothly water-worn). Crystal Structure: Microcrystalline to trigonal. Cleavage: None, conchoidal fracture.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or secondary silica deposition in igneous rock fractures. Smoothly rounded and polished over time by coastal wave action and natural abrasion on ocean beaches.
Uses & applications
Popular for lapidary work, rock tumbling, decorative landscaping, garden pebbles, stress stones, and craft projects.
Geological facts
Smooth beach stones like this are natural examples of hydro-abrasion. Over hundreds or thousands of years, wave action tumbles rocks against sand, creating a naturally smooth, tumbled surface without synthetic polish.
Field identification & locations
Identify by its exceptionally smooth, water-worn rounded shape, hardness (it will easily scratch glass), and subtle quartz veins or bands running across the surface. Common on coastal beaches, riverbeds, and gravel deposits worldwide.
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