mineral

Gray Agate

Chalcedony (Silicon Dioxide, SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Gray, bluish-gray, or translucent white with occasional banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: Uneven/Conchoidal; Specific Gravity: 2.58-2.64.

Hardness: 6
Luster: Waxy to vitreous

Identified June 24, 2026More mineral →

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Physical properties

Formation & geological history

Agate forms as a secondary mineral in volcanic rock cavities (vesicles) through the deposition of silica from groundwater. This process can take millions of years, often occurring in Cenozoic era basaltic or rhyolitic rocks.

Uses & applications

Commonly used in jewelry (beads, cabochons), ornamental items, tumbled stones for meditation, and industrial applications like mortar and pestles due to its hardness and chemical resistance.

Geological facts

Agate is a variety of chalcedony. The name comes from the Achates River in Sicily, where it was first discovered in ancient times. Gray agate is often associated with stability and grounding in metaphysical practices.

Field identification & locations

Identified in the field by its waxy luster, conchoidal fracture (curved breaks), and hardness (it will scratch glass). Often found in riverbeds, beaches, or areas with ancient volcanic activity such as Brazil, Uruguay, and India.