mineral

Polished pink-and-gray agate/chalcedony pebble

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

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; translucent gray-white and salmon-pink zones, waxy to vitreous luster, cryptocrystalline structure, and no visible cleavage. The rounded, polished surface obscures natural banding, and the pink areas may contain hematite or limonite inclusions.

Identified August 29, 2026More mineral →

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Physical properties

Formation & geological history

Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing successive layers of chalcedony and quartz; iron impurities create pink-red colors. Most examples formed during the Cenozoic or older volcanic episodes, depending on locality.

Uses & applications

Used for tumbled stones, cabochons, carvings, ornaments, and low-cost jewelry; durable agate is also used for beads and decorative objects.

Geological facts

Agate is a variety of chalcedony distinguished by internal color or texture banding, although some pieces are nearly patternless. Its colors can be natural or enhanced by dyeing or heat treatment.

Field identification & locations

Identify it by its glassy/waxy appearance, excellent polish, hardness, translucency, and possible curved color bands; it should resist scratching by a steel knife. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.