mineral

Likely quartz-rich chalcedony or agate fragment

Microcrystalline quartz (SiO₂), possibly iron-oxide-stained chalcedony/agate

AI-generated identification · may be incorrect

Small broken or tumbled fragment with translucent gray-white silica and a conspicuous yellow-orange iron-oxide or ochre-colored area. Quartz has Mohs hardness 7, vitreous to waxy luster, no cleavage, and conchoidal fracture; exact texture is difficult to confirm from the photograph.

Identified September 21, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed when silica-rich groundwater filled cavities or fractures in volcanic rock, with later iron staining. Such material is common in southern Brazil, including basalt-associated geodes and agates of the Paraná volcanic province, broadly compatible with the reported location.

Uses & applications

Used for cabochons, beads, polished specimens, and lapidary ornaments; this very small fragment has little commercial value.

Geological facts

The yellow-orange color may be limonite/goethite or iron-rich clay rather than a separate gemstone. A scratch test with steel is not diagnostic because quartz should scratch ordinary glass.

Field identification & locations

Inspect under magnification for banding, fibrous chalcedony, or tiny quartz crystals; test hardness against glass and check for a waxy fracture. Approximate value: $1–$10 as an unidentified fragment, potentially $10–$30 if attractive, confirmed agate/chalcedony.