gemstone

Polished agate/chalcedony pebble

Microcrystalline quartz (SiO₂), likely agate with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; cream to honey-yellow, translucent, and waxy to vitreous-lustrous with a smooth polished surface. Quartz is trigonal but occurs here as cryptocrystalline chalcedony; the rusty brown areas are likely limonite/goethite inclusions.

Identified August 30, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and quartz in layers; iron-bearing fluids create orange-brown staining. The specimen’s exact geological age and locality cannot be determined from the image.

Uses & applications

Used for cabochons, beads, carvings, tumblestones, and ornamental objects; durable enough for some small decorative or lapidary applications.

Geological facts

Agate is commonly recognized by curved or concentric banding, though this piece is mostly translucent chalcedony with patchy inclusions rather than strong bands.

Field identification & locations

Identify by its glassy/waxy luster, translucency, conchoidal fracture, lack of cleavage, and ability to scratch ordinary glass; it should not fizz in dilute acid. Common worldwide, especially Brazil, Uruguay, India, Madagascar, Mexico, and the western United States.