mineral

Moss Agate

Silicon Dioxide (SiO2) with inclusions of Manganese or Iron oxide

Hardness: 6.5–7 (Mohs scale); Color: Clear or milky white with green, black, or red moss-like dendritic inclusions; Luster: Vitreous to waxy; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.64

Hardness: 6
Luster: Vitreous to waxy

Identified March 17, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica in cavities of volcanic rocks or within limestone. The 'moss' patterns are dendrites created by mineral impurities like manganese or iron that crystallized into branching patterns as the agate formed. Most deposits are found in Cenozoic era basaltic flows.

Uses & applications

Predominantly used in jewelry (cabochons, beads, pendants), ornamental carvings, and as a popular specimen for collectors and holistic practitioners.

Geological facts

Despite its name, Moss Agate does not contain organic plant matter; the 'moss' is purely mineral. It has been historically known as the 'Agate of Gai' and was highly valued by ancient 18th-century European farmers as a luck charm for healthy crops.

Field identification & locations

Identify in the field by its semi-translucent chalcedony base and distinctive branching, organic-looking dark green patterns. Commonly found in India, Brazil, Uruguay, and the United States (specifically the Yellowstone River area/Montana Agate).

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