igneous
Black polished/tumbled stone, likely basalt or black jasper
Most likely fine-grained basalt (plagioclase and pyroxene); appearance can also match microcrystalline quartz (black jasper)
AI-generated identification · may be incorrectHardness approximately 5.5–7 Mohs depending on identity; opaque black, smooth rounded surface, vitreous to waxy luster, and no visible cleavage or crystals. The strong polish and uniform color prevent confident identification from the photograph alone.
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Physical properties
Hardness approximately 5.5–7 Mohs depending on identity; opaque black, smooth rounded surface, vitreous to waxy luster, and no visible cleavage or crystals. The strong polish and uniform color prevent confident identification from the photograph alone.
Formation & geological history
Basalt forms when mafic lava cools rapidly at or near Earth’s surface, commonly from the Cenozoic to present; black jasper forms by silica-rich replacement or cementation. Common sources include volcanic regions worldwide and commercial lapidary suppliers.
Uses & applications
Used as a tumbled decorative stone, paperweight, jewelry bead, and carving material; basalt is also widely used for aggregate and construction stone.
Geological facts
A steel file or quartz scratch test helps distinguish them: basalt is usually scratched by quartz, whereas jasper is not. A streak test, density measurement, and close examination of edges would improve identification.
Field identification & locations
Look for very fine grain, dull-to-glassy black surfaces, and occasional tiny gray crystals for basalt; jasper is typically denser and more uniformly waxy. Common localities include India, China, Mexico, Brazil, and volcanic areas worldwide.
