igneous
Rhyolitic jasper or iron-stained chert
Microcrystalline quartz (SiO₂), likely with hematite/goethite staining
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; reddish-brown, gray, and cream mottling; dull to slightly waxy luster; dense, cryptocrystalline texture with irregular/conchoidal fracture and no obvious cleavage.
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Physical properties
Hardness about 6.5–7 Mohs; reddish-brown, gray, and cream mottling; dull to slightly waxy luster; dense, cryptocrystalline texture with irregular/conchoidal fracture and no obvious cleavage.
Formation & geological history
Likely silica-rich volcanic material or chemically precipitated chert later stained by iron oxides; exact age and origin cannot be determined from the photograph. Such material forms in volcanic flows, silica-rich cavities, or sedimentary beds.
Uses & applications
Used as lapidary rough, cabochons, beads, and decorative stone; generally unsuitable for structural construction in small specimens.
Geological facts
The fine texture can resemble jasper, chert, or silicified rhyolite, and these names often overlap commercially. A fresh fracture should be glassy or subtly conchoidal rather than granular.
Field identification & locations
Commonly found in volcanic and sedimentary terrains worldwide, including the western United States. Test with a steel file or quartz: it should resist scratching by steel and may scratch ordinary glass; inspect for a waxy surface and silica fracture.
