mineral

Tumbled chalcedony or agate

Microcrystalline quartz (SiO₂), likely chalcedony with iron-oxide staining

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent gray-brown to honey color with waxy-to-dull luster and no obvious cleavage. It appears naturally fractured or roughly shaped, with possible fine banding obscured by weathering.

Identified August 23, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, precipitating microcrystalline quartz over long periods; the specimen’s exact geological age and locality cannot be determined from the image.

Uses & applications

Used as an ornamental stone, carving material, lapidary rough, and occasionally in jewelry; this piece appears more suitable for collecting or display than high-grade gem cutting.

Geological facts

Chalcedony is quartz composed of microscopic intergrowths of quartz varieties; iron oxides commonly create brown, orange, or reddish coloration.

Field identification & locations

Identify it by its waxy appearance, translucency, lack of cleavage, and ability to scratch glass; acid does not effervesce. Common sources include volcanic terrains in Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.