mineral

Polished chalcedony (likely moss/ag ate)

Microcrystalline quartz, SiO₂; probable moss agate or jasper variety

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent cream, honey-yellow, gray, and brown coloration with cloudy or dendritic inclusions; waxy to vitreous luster, cryptocrystalline structure, and no visible cleavage. Rounded and glossy from polishing.

Identified September 6, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, depositing chalcedony and iron/manganese-stained inclusions. Such agates commonly formed during the Cenozoic or older volcanic episodes, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and inexpensive jewelry; attractive patterned pieces are popular among collectors.

Geological facts

Moss agate’s plant-like patterns are mineral inclusions rather than fossils or organic material. Yellow-brown tones commonly reflect iron oxides or hydroxides.

Field identification & locations

Identify by its waxy luster, translucency at thin edges, hardness, and conchoidal fracture; it should resist scratching by a steel knife. Common sources include Oregon, Montana, India, Brazil, Uruguay, and Madagascar.