gemstone

Agate

Silicon dioxide (Chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, microcrystalline quartz structure with distinctive banded patterns, conchoidal fracture, and specific gravity around 2.60 to 2.65. Colors range across white, yellow, orange, red, brown, and grey.

Identified August 6, 2026More gemstone →

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Physical properties

Formation & geological history

Formed mainly in cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater solutions, often in concentric layers over long geological periods.

Uses & applications

Widely used in jewelry, decorative ornaments, gemstone carvings, and industrial applications requiring durable precision instruments due to its chemical resistance.

Geological facts

Agate was highly prized by ancient civilizations such as the Greeks and Egyptians for use in signet rings, seals, and protective amulets. It is named after the Achates River in Sicily where it was found in antiquity.

Field identification & locations

Easily identified by its characteristic translucent banding and high scratch resistance (hardness). Commonly found worldwide in volcanic regions, riverbeds, and gravel deposits.