mineral
Tumbled amber-colored agate or jasper
Microcrystalline quartz (SiO₂), likely chalcedony with iron-oxide inclusions
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; dark brown to black with translucent amber-brown areas, waxy-to-glassy luster, and no visible cleavage. It has a cryptocrystalline quartz structure and rounded, polished surfaces from tumbling.
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Physical properties
Hardness about 6.5–7 Mohs; dark brown to black with translucent amber-brown areas, waxy-to-glassy luster, and no visible cleavage. It has a cryptocrystalline quartz structure and rounded, polished surfaces from tumbling.
Formation & geological history
Formed when silica-rich groundwater deposited chalcedony in cavities or fractures, with iron oxides producing the brown coloration; typically Paleozoic to Cenozoic in age depending on locality.
Uses & applications
Used as a decorative tumbled stone, cabochon, bead, or paperweight; attractive pieces may be collected, though this specimen appears commercially polished rather than gem grade.
Geological facts
The appearance may also overlap with common brown jasper or opaque agate; transmitted light showing internal banding would support agate identification.
Field identification & locations
Common in volcanic terrains and alluvial gravel deposits worldwide, especially Brazil, Uruguay, Mexico, India, Madagascar, and the western United States. Check translucency, curved fracture, and hardness; it should scratch glass but not quartz.
