igneous
Polished black stone specimen, likely black basalt or diabase
Basalt/diabase; chiefly plagioclase feldspar and pyroxene, possibly magnetite
AI-generated identification · may be incorrectDark gray to black, fine-grained, opaque, with a dull to faintly vitreous luster; typical Mohs hardness 5–6, no visible cleavage, and specific gravity about 2.8–3.1. The sharply faceted, uniform surface indicates cutting and polishing rather than natural crystal faces.
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Physical properties
Dark gray to black, fine-grained, opaque, with a dull to faintly vitreous luster; typical Mohs hardness 5–6, no visible cleavage, and specific gravity about 2.8–3.1. The sharply faceted, uniform surface indicates cutting and polishing rather than natural crystal faces.
Formation & geological history
Basalt forms when mafic lava cools rapidly at or near Earth’s surface; diabase is its shallow intrusive equivalent. Such rocks range from Precambrian to modern, but the specimen’s age cannot be determined visually.
Uses & applications
Used as aggregate, paving stone, monuments, countertops, and decorative or lapidary objects; this appears to be a polished display or carved piece rather than a natural outcrop sample.
Geological facts
Its very uniform black appearance could also represent manufactured or coated stone, so identification from the image is provisional. A magnet, streak, and fresh unpolished edge would help distinguish basalt/diabase from other dark materials.
Field identification & locations
Look for tiny interlocking feldspar/pyroxene grains, substantial weight, and no fizz with dilute hydrochloric acid. Common sources include volcanic regions worldwide, especially India, China, Iceland, and the western United States.
