mineral
Tumbled gray stone, likely gray agate or jasper
Microcrystalline quartz (chalcedony), SiO₂; exact identification requires testing
AI-generated identification · may be incorrectSmoothly polished, opaque-to-translucent gray-brown body with cream linear banding or fractures and a waxy-to-glassy luster. Quartz hardness is about 7 Mohs; no obvious cleavage, cryptocrystalline structure, and specific gravity near 2.6.
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Physical properties
Smoothly polished, opaque-to-translucent gray-brown body with cream linear banding or fractures and a waxy-to-glassy luster. Quartz hardness is about 7 Mohs; no obvious cleavage, cryptocrystalline structure, and specific gravity near 2.6.
Formation & geological history
Likely formed when silica-rich groundwater filled cavities or fractures in volcanic rock, later producing chalcedony bands; geological age is unknown and depends on its source deposit.
Uses & applications
Used as a lapidary stone for tumbling, cabochons, beads, and decorative objects; not typically used in construction as an individual specimen.
Geological facts
The pale lines may be natural agate banding, healed fractures, or veins, though the photograph cannot distinguish them reliably from similar jasper or quartzite.
Field identification & locations
Commonly found in volcanic terrains and gravel deposits worldwide, especially Brazil, Uruguay, Mexico, India, and the western United States. A scratch test, translucency check, and close examination of banding can help confirm chalcedony.
