sedimentary

Iron-rich chert or jasper fragment

Microcrystalline quartz (SiO₂), commonly hematite/goethite-bearing

AI-generated identification · may be incorrect

Angular, dense dark brown-gray fragment with rusty orange-red iron-oxide staining and a dull to slightly waxy luster. Likely hardness ~6.5–7 Mohs, no obvious cleavage, and conchoidal fracture; exact texture is partly obscured by weathering.

Identified August 10, 2026More sedimentary →

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Physical properties

Formation & geological history

Probably a silica-rich sedimentary rock formed from microcrystalline quartz, later stained or cemented by iron oxides during weathering. The Budapest-region prior is plausible: similar siliceous and iron-stained gravels can occur in transported sediments, though an exact locality cannot be established visually.

Uses & applications

Mostly a collecting or educational specimen; attractive pieces may be cut or polished for cabochons and decorative stone. It has little commercial value at this size.

Geological facts

The rusty colors typically reflect hematite and/or goethite, while the dark matrix may contain manganese oxides or other impurities. A steel file should barely scratch it, whereas quartz will scratch glass.

Field identification & locations

Field identification: test for glass-scratching hardness, look for conchoidal fracture, and check whether the red-brown coloration is internal rather than superficial soil. Commonly found as rounded to angular pieces in gravels and weathered silica-rich beds; acid testing is generally nonreactive.