gemstone

Polished carnelian/chalcedony

Cryptocrystalline quartz (SiO₂), likely banded agate with carnelian zones

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; translucent honey-brown to orange with gray-black curved banding and vitreous-to-waxy luster. Quartz has a trigonal crystal structure, but the specimen is microcrystalline and shows no visible cleavage.

Identified September 17, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing chalcedony and iron-colored quartz bands. Individual agates may range from Paleozoic to Cenozoic in age, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, and ornamental polished stones; also a common lapidary and collector material.

Geological facts

The orange color is typically caused by finely dispersed iron oxides. Its curved internal bands and conchoidal fracture are characteristic of agate/chalcedony rather than jasper or glass.

Field identification & locations

Common in volcanic terrains, especially Brazil, Uruguay, India, Madagascar, Mexico, and the western United States. Field identification: glassy or waxy surface, strong polish, hardness that can scratch ordinary glass, and curved banding; acid does not react.