mineral
Polished jasper/chalcedony nodule
Microcrystalline quartz (SiO₂), likely jaspery chalcedony with iron-oxide staining
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; cream, tan, brown, and gray coloration with a waxy to glassy polish and opaque-to-slightly translucent zones. No obvious cleavage; dense, cryptocrystalline quartz texture and typical specific gravity around 2.6.
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Physical properties
Hardness about 6.5–7 Mohs; cream, tan, brown, and gray coloration with a waxy to glassy polish and opaque-to-slightly translucent zones. No obvious cleavage; dense, cryptocrystalline quartz texture and typical specific gravity around 2.6.
Formation & geological history
Silica-rich groundwater filled cavities or replaced host rock, while iron oxides produced the brown and yellow patterns; the specimen was subsequently rounded and polished. Its exact geological age cannot be determined visually and depends on the source deposit.
Uses & applications
Used as a decorative polished stone, worry stone, cabochon, or lapidary material; jasper and chalcedony are also used in beads and carvings.
Geological facts
The rounded shape may be natural alluvial wear or deliberate lapidary shaping. A strong glass scratch test should not mark it, while quartz can scratch ordinary glass.
Field identification & locations
Common sources include Brazil, Madagascar, India, Indonesia, and the western United States. Confirm with a streak test, hardness test, and close examination for quartz-like translucency; exact identification may require specific-gravity or microscopy testing.
