mineral

Agate

Silicon dioxide (SiO2)

Hardness: 6.5–7 (Mohs scale); Color: Variegated brown, grey, and white; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None/Conchoidal fracture; Specific gravity: 2.58–2.64

Hardness: 6
Color: Variegated brown, grey, and white
Luster: Waxy to vitreous

Identified April 6, 2026More mineral →

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Physical properties

Formation & geological history

Formed primarily within volcanic or metamorphic rocks through the deposition of silica from groundwater into cavities or vesicles. This specific tumbled specimen displays characteristic concentric banding.

Uses & applications

Used widely in lapidary arts, jewelry, ornaments, and precision industrial tools like chemical mortars and pestles due to its hardness and resistance to acids.

Geological facts

Agate is a variety of chalcedony. It was named by Theophrastus, a Greek philosopher, who discovered the stone along the shore line of the Dirillo River in Sicily.

Field identification & locations

Identify in the field by its translucent properties when held to light and its distinctive banding. Commonly found in gravel beds of rivers or ancient volcanic sites globally.