mineral

Polished black stone, likely black jasper or basalt

Probable microcrystalline quartz (SiO₂) jasper; basalt is an alternative

AI-generated identification · may be incorrect

Smooth tumbled surface with dark brown-black color and vitreous to waxy luster; likely hardness 6.5–7 if jasper, or about 6 if basalt. No visible crystals or cleavage; apparent density is moderate to high.

Identified August 21, 2026More mineral →

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Physical properties

Formation & geological history

Black jasper forms when silica-rich fluids replace or cement rock, while basalt forms from rapidly cooled mafic lava, commonly younger than a few hundred million years. The specimen has been mechanically tumbled and polished.

Uses & applications

Used as a decorative stone, cabochon, bead, worry stone, or inexpensive collectible; basalt is mainly used for aggregate and construction rather than jewelry.

Geological facts

The photograph does not show diagnostic features sufficient for a certain identification. A glassy streak, conchoidal fracture, and no reaction to dilute acid would favor jasper; tiny crystals and a gray-black streak would favor basalt.

Field identification & locations

Common sources include India, Madagascar, Brazil, Mexico, and volcanic regions worldwide. Test hardness against glass and inspect a fresh edge; avoid relying on color alone.