gemstone

Tumbled carnelian agate

Cryptocrystalline chalcedony (SiO₂), an iron-colored variety of agate

AI-generated identification · may be incorrect

Typically orange-brown to reddish, translucent, with vitreous/waxy luster and subtle curved banding or clouding; hardness 6.5–7 Mohs, no cleavage, conchoidal fracture, and specific gravity about 2.6. The smooth rounded surface indicates tumbling and polishing.

Identified August 8, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and iron oxides in layers; most deposits are Cenozoic to older, depending on locality. Common sources include India, Brazil, Uruguay, Madagascar, and Botswana.

Uses & applications

Used for beads, cabochons, carvings, ornaments, and inexpensive jewelry; polished pieces are popular for collecting and lapidary work.

Geological facts

Carnelian’s red-orange color comes mainly from finely dispersed hematite or goethite. Heating can intensify or redden the color, and dyed imitations are also common.

Field identification & locations

Identify it by its warm orange-brown color, translucency, waxy polish, conchoidal fracture, and lack of visible large crystals; a glass imitation may show bubbles or unnaturally uniform color. A small tumbled piece commonly sells for $1–$10; distinctive natural banding or larger quality specimens may reach $15–$50.