igneous
Black tumbled stone, likely basalt or black jasper
Most consistent with fine-grained basalt (mainly plagioclase and pyroxene); exact identification requires testing
AI-generated identification · may be incorrectOpaque black, smoothly rounded and low-gloss from tumbling; likely hardness 5–6.5 Mohs, fine-grained with no visible crystals, and specific gravity roughly 2.8–3.1.
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Physical properties
Opaque black, smoothly rounded and low-gloss from tumbling; likely hardness 5–6.5 Mohs, fine-grained with no visible crystals, and specific gravity roughly 2.8–3.1.
Formation & geological history
Basalt forms when mafic lava rapidly cools at or near Earth’s surface, commonly in volcanic fields and oceanic crust; ages range from recent eruptions to Precambrian specimens.
Uses & applications
Used as aggregate, paving stone, landscaping material, and decorative tumbled stone. This small piece has minimal commercial value.
Geological facts
The photograph cannot distinguish basalt from black jasper, obsidian, magnetite-rich rock, or manufactured slag. Basalt is generally nonmetallic and does not show the glassy conchoidal fracture typical of obsidian.
Field identification & locations
Look for a dull-to-subtle luster and tiny crystalline texture; a streak, magnet test, hardness test, and specific-gravity measurement would help. Common sources include volcanic regions worldwide.
