sedimentary
Agate (Chalcedony Pebble)
Silicon Dioxide (SiO2)
Hardness 6.5-7 on the Mohs scale, yellowish-tan to translucent honey color, waxy to vitreous luster, microcrystalline/cryptocrystalline quartz structure, no cleavage, specific gravity around 2.58-2.64.
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Physical properties
Hardness 6.5-7 on the Mohs scale, yellowish-tan to translucent honey color, waxy to vitreous luster, microcrystalline/cryptocrystalline quartz structure, no cleavage, specific gravity around 2.58-2.64.
Formation & geological history
Formed by the precipitation of silica-rich fluids inside cavities of volcanic rocks or weathered sedimentary deposits over millions of years.
Uses & applications
Used for lapidary arts, jewelry making, tumbled stones, ornamental carvings, and decorative aggregate.
Geological facts
Agate is a banded variety of microcrystalline quartz. Small river-worn pebbles like this one often show subtle translucent banding or cloudiness when backlit.
Field identification & locations
Can be identified by its conchoidal fracture, hard surface that scratches steel, and translucent yellow-brown color. Commonly found in riverbeds, gravel pits, and ancient volcanic regions worldwide.
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