Rock Identifier
Tumbled carnelian/chalcedony pebbles (Chalcedony, microcrystalline quartz (SiO₂), likely iron-colored carnelian) — gemstone
gemstone

Tumbled carnelian/chalcedony pebbles

Chalcedony, microcrystalline quartz (SiO₂), likely iron-colored carnelian

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; orange to honey-brown, translucent to opaque, waxy/glassy luster, and no visible cleavage. The rounded surfaces indicate mechanical tumbling and polishing.

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Physical properties

Hardness about 6.5–7 Mohs; orange to honey-brown, translucent to opaque, waxy/glassy luster, and no visible cleavage. The rounded surfaces indicate mechanical tumbling and polishing.

Formation & geological history

Chalcedony forms when silica-rich groundwater fills cavities and fractures, commonly in volcanic rocks; iron oxides produce the orange-red coloration. Deposits range from Paleozoic to recent, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, tumbled stones, and ornamental objects; durable enough for jewelry and small decorative work.

Geological facts

Carnelian is the orange-red variety of chalcedony, while paler honey-colored material may be called orange chalcedony. Heat treatment can intensify its color.

Field identification & locations

Identify it by its uniform cryptocrystalline texture, waxy luster, translucency, and lack of cleavage; it should scratch glass but not be scratched by a steel knife. Common sources include Brazil, Uruguay, India, Madagascar, and the United States.