gemstone

Polished carnelian agate

Chalcedony (microcrystalline quartz), SiO₂, colored mainly by iron oxides

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent orange to reddish-brown with darker brown/black inclusions, vitreous-to-waxy luster, and no visible cleavage. Its quartz crystals are microscopic and fibrous, giving a smooth, tough texture.

Identified August 21, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks and deposits chalcedony in layers; iron produces the orange-red color. Individual pieces commonly formed during the Cenozoic or older volcanic episodes, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, worry stones, and decorative objects; durable and inexpensive compared with precious gemstones.

Geological facts

The orange variety is called carnelian, while banding or contrasting chalcedony may be marketed as agate. Heat treatment can intensify its red-orange color.

Field identification & locations

Identify by its translucent orange body, waxy luster, lack of cleavage, and ability to scratch glass; a gemological test can distinguish it from dyed glass or resin. Common sources include India, Brazil, Uruguay, Madagascar, and the United States.