mineral

Moss Agate

Chalcedony (SiO2) with inclusions of manganese or iron oxides

Hardness: 6.5–7 on the Mohs scale; Color: Clear to milky white with dark green, black, or red dendritic (tree-like) inclusions; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific gravity: 2.58–2.64.

Hardness: 6
Luster: Vitreous to waxy

Identified March 23, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the weathering of volcanic rocks (igneous host). Silica-rich fluids fill cavities and cracks where mineral oxides crystalize into branch-like patterns over thousands of years. Found in Cenozoic era deposits.

Uses & applications

Primarily used in jewelry (cabochons, beads), decorative carvings, and as a popular specimen for crystal collectors. Historically used as talismans and in agriculture to promote crop growth.

Geological facts

Despite its name, Moss Agate contains no organic moss; the 'vegetation' patterns are actually chemical impurities like hornblende. It was historically known as the 'Mocha Stone' because it was traded through the port of Mocha in Yemen.

Field identification & locations

Identify in the field by its translucent body combined with opaque, branching green or black inclusions. It is commonly found in India, Brazil, the USA (Montana/Oregon), and Uruguay. Collectors should look for high transparency and vivid patterns.

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