mineral
Chalcedony (Agate / Quartz Pebble)
Silicon Dioxide (SiO2)
Hardness 6.5-7 on the Mohs scale, waxy to vitreous luster, translucent to semi-opaque white to milky body with reddish-brown iron-oxide inclusions, trigonal/microcrystalline structure, conchoidal fracture, specific gravity around 2.6.
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Physical properties
Hardness 6.5-7 on the Mohs scale, waxy to vitreous luster, translucent to semi-opaque white to milky body with reddish-brown iron-oxide inclusions, trigonal/microcrystalline structure, conchoidal fracture, specific gravity around 2.6.
Formation & geological history
Formed through the deposition of silica-rich water solutions at low temperatures in cavities, fissures, or weathered host rocks, often associated with volcanic activity or secondary sedimentary weathering.
Uses & applications
Used widely for lapidary arts, jewelry making, tumbling, cabochons, and decorative ornamental carvings.
Geological facts
Microcrystalline quartz minerals like chalcedony were among the earliest raw materials used by ancient humans to craft tools and arrowheads due to their predictable conchoidal fracture and sharpness.
Field identification & locations
Identify in the field by its waxy luster, hardness (will scratch glass), smooth river-worn surface, and light translucency. Commonly found in stream beds, gravel bars, and volcanic terrains worldwide.
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