gemstone

Dark polished cabochon, possibly onyx or black agate

Unidentified cryptocrystalline quartz; potentially chalcedony (SiO₂)

AI-generated identification · may be incorrect

Small, opaque, dark blue-black polished oval with a glossy luster; the image is too blurry to determine material, hardness, or internal structure. If chalcedony, hardness is about 6.5–7 Mohs and its crystal structure is microcrystalline quartz.

Identified October 10, 2026More gemstone →

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Physical properties

Formation & geological history

If quartz chalcedony, it formed as silica-rich fluids filled cavities or fractures, with age depending on its host rock. The setting and specimen’s exact geological origin cannot be determined from the image.

Uses & applications

Likely used as jewelry, possibly a ring stone; dark cabochons are also collected and used decoratively.

Geological facts

Black onyx is commonly dyed chalcedony, while similar-looking stones may be glass or other materials; a clear image or tests would be needed to distinguish them.

Field identification & locations

The image shows a mounted, polished stone, but provides insufficient detail for reliable identification. Check hardness and inspect under magnification; avoid destructive tests on jewelry.