mineral
Polished dark agate or jasper sphere
Microcrystalline quartz (chalcedony), SiO₂; possibly iron-rich jasper
AI-generated identification · may be incorrectVery smooth, spherical polish with dark brown-black translucent areas and reddish-orange patches; vitreous luster. Quartz hardness is about 7 Mohs, with no visible cleavage and conchoidal fracture; exact identification requires testing because the image shows a highly polished specimen.
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Physical properties
Very smooth, spherical polish with dark brown-black translucent areas and reddish-orange patches; vitreous luster. Quartz hardness is about 7 Mohs, with no visible cleavage and conchoidal fracture; exact identification requires testing because the image shows a highly polished specimen.
Formation & geological history
Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and iron oxides in bands or breccia; commonly Paleozoic to Cenozoic, though age depends on locality. It was later cut and polished into a sphere.
Uses & applications
Used as an ornamental sphere, paperweight, decorative object, and lapidary specimen; similar agate and jasper spheres commonly sell for about $15–$100, with larger or unusually patterned pieces reaching $150+.
Geological facts
Dark red-brown coloration commonly comes from hematite or goethite inclusions. Strong translucency at edges and curved banding would favor agate; opaque, irregular red-black patterns favor jasper.
Field identification & locations
Common sources include Brazil, Uruguay, Madagascar, Mexico, India, and the United States. Check hardness with caution, inspect edges for translucency or banding, and use a loupe; a mineral streak, refractive-index, or specific-gravity test is needed for certainty.
