gemstone

Polished carnelian agate cabochon

Microcrystalline quartz (chalcedony), SiO₂, colored mainly by iron oxides

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent orange-red to reddish brown, vitreous to waxy luster, cryptocrystalline structure, no visible cleavage, specific gravity about 2.58–2.64. The oval cabochon appears polished and may contain natural pits or inclusions.

Identified September 15, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, with iron producing the orange-red color; commonly Cenozoic to older, depending on its host rock. It is found worldwide, notably in India, Brazil, Uruguay, Madagascar, Botswana, and the United States.

Uses & applications

Used for beads, cabochons, carvings, seals, and ornamental objects; durable enough for jewelry but less valuable than fine transparent gems.

Geological facts

Carnelian is an orange-red variety of chalcedony and grades into sard when darker brown-red. Strong, even color and translucency generally increase desirability.

Field identification & locations

Identify by its waxy luster, translucency, lack of cleavage, and hardness sufficient to scratch glass; natural banding may be subtle. This specimen’s bright, uniform color and rounded polish could also indicate heat treatment or dye enhancement.