igneous
Small tumbled dark stone, possibly basalt or slag
Likely fine-grained basalt; exact identification is uncertain from the photograph
AI-generated identification · may be incorrectDark gray-blue, smoothly tumbled, with a dull to slightly satin luster; likely composed mainly of plagioclase and pyroxene, with Mohs hardness about 5–6 and no visible cleavage. The rounded shape indicates polishing or natural abrasion.
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Physical properties
Dark gray-blue, smoothly tumbled, with a dull to slightly satin luster; likely composed mainly of plagioclase and pyroxene, with Mohs hardness about 5–6 and no visible cleavage. The rounded shape indicates polishing or natural abrasion.
Formation & geological history
If basalt, it formed from rapidly cooled mafic lava, commonly during the Cenozoic or older volcanic episodes. Its smooth form likely resulted from tumbling, beach abrasion, or stream transport.
Uses & applications
Used as a decorative pebble, lapidary material, or inexpensive cabochon; basalt itself is widely used as aggregate and building stone.
Geological facts
Basalt is the most common volcanic rock on Earth and commonly contains tiny crystals invisible without magnification. The specimen could also be industrial slag or another dark stone, which cannot be excluded visually.
Field identification & locations
Test for a glassy versus crystalline texture with magnification, streak on unglazed ceramic, and compare density; basalt is typically heavy and leaves a gray streak. Common sources include volcanic regions and manufactured tumbling supplies.
