mineral

Polished plume agate

Chalcedony (microcrystalline quartz), SiO₂, with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent gray, olive, cream, and reddish-brown colors with feathery or moss-like iron inclusions; vitreous to waxy luster, no cleavage, conchoidal fracture, trigonal quartz structure. The pictured piece is tumbled and polished.

Identified September 21, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, commonly during Cenozoic volcanic activity; later iron and manganese oxides create plume patterns. Exact age and locality cannot be determined from the image.

Uses & applications

Used for cabochons, carvings, ornaments, lapidary specimens, and jewelry; valued primarily for attractive pattern and polish rather than rarity.

Geological facts

“Plume agate” describes the inclusion pattern, not a separate mineral species. Red-brown coloration commonly comes from hematite or limonite, while dark areas may reflect manganese oxides or dense inclusions.

Field identification & locations

Identify by its glassy polish, translucent chalcedony body, hardness, and internal branching or plume-like inclusions; common sources include Mexico, Oregon, Montana, Brazil, and Indonesia. Avoid confusing it with dyed glass or jasper, which lacks natural translucency and conchoidal fracture.