mineral

Agate (Plume/Moss variety)

Cryptocrystalline Quartz (SiO2) with iron/manganese inclusions

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Gray, white, translucent with red and earthy-brown 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 June 21, 2026More mineral →

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Physical properties

Formation & geological history

Formed in cavities of volcanic or metamorphic rocks when silica-rich groundwater precipitates over long periods. The colorful inclusions are often caused by oxides of iron or manganese during the crystallization process.

Uses & applications

Used extensively in jewelry (cabochons), lapidary arts, ornamental carving, and as a semi-precious collector gemstone.

Geological facts

Agate is a variety of chalcedony. The specific 'mossy' or 'plume' patterns seen in this specimen are created by mineral impurities that grow in dendritic or cloud-like formations within the host silica.

Field identification & locations

Identify by its waxy luster, conchoidal fracture (curved breaks like glass), and its ability to scratch glass. Commonly found in riverbeds or volcanic regions like the American West (Oregon, Montana) and Brazil.