gemstone

Agate

Silicon dioxide (Chalcedony), SiO2

Hardness: 6.5 to 7 on the Mohs scale. Color: Brown, translucent to opaque. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline quartz). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.58 to 2.64.

Hardness: 6
Color: Brown, translucent to opaque
Luster: Waxy to vitreous

Identified August 5, 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

Used in ornamental objects, jewelry, as a gemstone, and in industrial applications such as mortars and pestles due to its durability.

Geological facts

Agate is a banded variety of chalcedony. The bands visible in many specimens reflect successive layers of deposition in a cavity.

Field identification & locations

Can be identified in the field by its waxy luster, hardness that scratches glass, and sometimes subtle translucent banding. Found worldwide, particularly in volcanic regions.