gemstone

Agate (Tumbled)

Silicon Dioxide (Chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, colors range from grey to brown with banded or mottled patterns, specific gravity of 2.60 to 2.65, conchoidal fracture with no true cleavage.

Identified July 28, 2026More gemstone →

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Physical properties

Formation & geological history

Formed primarily within the cavities of volcanic and metamorphic rocks through the slow deposition of silica-rich groundwater solutions over millions of years.

Uses & applications

Commonly used in tumbled stones, cabochons, jewelry, decorative carvings, and as collectible lapidary specimens.

Geological facts

Agate has been used since ancient times for gemstones, seals, and amulets. The Greeks and Romans valued it for its supposed medicinal properties and protective qualities.

Field identification & locations

Identified by its waxy luster, hardness (scratches glass), and distinctive internal banding or translucent mottled patterns. Found worldwide, particularly in Brazil, India, Madagascar, and the United States.