mineral
Quartz Pebble (Beach Agate / Chalcedony Pebble)
Silicon Dioxide (SiO2)
Mohs hardness of 7, translucent to semi-transparent milky or clear appearance, vitreous to waxy luster, conchoidal fracture pattern, hexagonal crystal structure (microcrystalline in chalcedony), specific gravity around 2.65.
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Physical properties
Mohs hardness of 7, translucent to semi-transparent milky or clear appearance, vitreous to waxy luster, conchoidal fracture pattern, hexagonal crystal structure (microcrystalline in chalcedony), specific gravity around 2.65.
Formation & geological history
Formed through precipitation of silica-rich fluids in cavities of igneous or sedimentary rocks, followed by erosion, stream transport, and natural tumbling by ocean or river waves over thousands of years.
Uses & applications
Used in lapidary work, jewelry making, tumbled stone collections, landscape decoration, and historically in glassmaking or abrasives.
Geological facts
Smooth beach pebbles like this undergo millions of natural impacts against sand and other stones in surf zones, which frost the surface and round the sharp edges.
Field identification & locations
Identified by its high hardness (scratches glass, steel cannot scratch it), smooth water-worn texture, conchoidal fracture marks, and translucent nature when held against light. Commonly found on gravel beaches, riverbeds, and glacial deposits worldwide.
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