gemstone

Agate

Silicon Dioxide (Chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, variable colors due to impurities (yellow, white, brown, grey), waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture, specific gravity around 2.60 to 2.65.

Identified July 29, 2026More gemstone →

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Physical properties

Formation & geological history

Formed mainly in cavities of volcanic rocks or ancient lavas through the deposition of silica-rich groundwater solutions over millions of years.

Uses & applications

Used primarily in jewelry, ornamental carvings, decorative objects, and precision instruments like mortars and pestles due to its hardness.

Geological facts

Agate is one of the most popular and varied ornamental stones, known for its distinct concentric banding patterns which record the rhythmic deposition of silica.

Field identification & locations

Found worldwide in volcanic regions, riverbeds, and weathered outcroppings. Easily identified by its hardness, waxy luster, and banded or translucent appearance.