mineral

Moss Agate

Chalcedony (Silicon Dioxide with inclusions) - SiO2

Hardness: 6.5–7 (Mohs scale); Color: Translucent white to clear with green, dendritic moss-like inclusions; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (Conchoidal fracture); Specific gravity: 2.58–2.64

Hardness: 6
Luster: Vitreous to waxy

Identified March 29, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica-rich groundwater in the fissures and cavities of volcanic igneous rocks (basalts). The 'moss' appearance is caused by manganese or iron oxide inclusions during the cooling process. Common in Cenozoic era deposits.

Uses & applications

Primary use is in jewelry (cabochons, beads), decorative carvings, and as a popular collector's specimen. Historically used as a 'healing stone' in various cultures and in early manufacturing of precision tools.

Geological facts

Despite its name, moss agate does not contain organic plant matter; the green patterns are strictly mineral. It is often referred to as the 'Gardener's Stone' and has been used since ancient times for amulets and ornaments. Famous deposits are found in the Yellowstone River area.

Field identification & locations

Identify in the field by its translucency coupled with dark green dendritic (branch-like) patterns that don't wash off. It will scratch glass but cannot be scratched by a steel knife. Common locations include India, Brazil, Uruguay, and the United States (Montana and Wyoming).

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