mineral

Moss Agate

Chalcedony (SiO2) with dendritic inclusions of Manganese or Iron oxide

Hardness: 6.5-7 (Mohs scale); Color: Translucent to milky white with green, brown, or red moss-like inclusions; Lustre: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.58-2.64.

Hardness: 6

Identified January 7, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica in cavities of igneous rocks such as basalt. The 'moss' patterns are dendritic inclusions of minerals like hornblende, manganese, or iron that branch out within the cooling silica gel. They can range from Cenozoic to much older depending on the host rock environment.

Uses & applications

Primarily used in jewelry (cabochons, beads, rings), as a decorative ornamental stone, and is highly valued by mineral collectors for its unique organic-looking patterns.

Geological facts

Despite its name, Moss Agate does not contain organic matter or real moss; the patterns are purely mineral-based. Historically, it was known as the 'Gardener's Stone' and was believed to ensure a bountiful harvest in medieval times.

Field identification & locations

Identify in the field by its translucent body combined with dark, tangled, or branching inclusions that look like plant life. It is commonly found in India, Brazil, the United States (specifically the Yellowstone River area), and Scotland. When held to a light source, the translucent chalcedony allows internal structures to become visible.

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