mineral

Polished plume agate

Chalcedony (microcrystalline SiO₂) with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent white, gray, pink, and reddish-brown with feathery dendritic/plume patterns, waxy to vitreous luster, cryptocrystalline structure, and no cleavage. The rounded triangular form is tumbled or polished.

Identified August 19, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater filled cavities in volcanic rock, depositing chalcedony and later iron/manganese oxides that produced the plume inclusions. Most agates formed during volcanic episodes from the Paleozoic through Cenozoic eras.

Uses & applications

Used for cabochons, beads, carvings, display pieces, and lapidary collections; it is generally an ornamental gemstone rather than an industrial stone.

Geological facts

Agate is a variety of banded or patterned chalcedony, and plume agate’s inclusions resemble moss, branches, feathers, or flames without being true fossils or organic material.

Field identification & locations

Identify it by its translucency, very fine silica texture, curved polished edges, and nonmetallic plume inclusions; common sources include Oregon, Idaho, Montana, Mexico, Brazil, and India. A steel file should not easily scratch it, though glass testing can damage the specimen.