mineral

Chalcedony (Agate / Moss Agate)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs. Color: Translucent greyish-blue, brown, and white with cloudy mineral inclusions. Luster: Waxy to vitreous. Crystal Structure: Microcrystalline (trigonal). Cleavage: None, exhibits conchoidal fracture. Specific Gravity: 2.58-2.64.

Hardness: 6
Luster: Waxy to vitreous

Identified July 24, 2026More mineral →

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Physical properties

Formation & geological history

Forms secondary mineral deposits in volcanic rock cavities or sedimentary rocks through precipitation of silica-rich hydrothermal fluids at low temperatures.

Uses & applications

Popular as a tumbled gemstone, in jewelry making (cabochons, beads), decorative carvings, and lapidary art.

Geological facts

Agates and chalcedony are composed of microscopic crystals of quartz intergrown with moganite. The inclusion patterns often resemble landscapes or moss, earning varieties names like moss agate or dendritic chalcedony.

Field identification & locations

Identified in the field by its hardness (scratches glass, resists steel), waxy finish, smooth rounded river-worn texture, and translucent light transmission. Commonly found along riverbeds, beaches, and weathered volcanic deposits worldwide.

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