metamorphic
Tumbled Slate or Basalt Pebble
Metamorphic fine-grained rock / Slate or Phyllite
Hardness varies from 3 to 6 depending on specific mineralogy, color is dark gray to black, luster is dull to sub-vitreous, texture is smooth due to water-rolling or tumbling, fine-grained crystal structure.
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Physical properties
Hardness varies from 3 to 6 depending on specific mineralogy, color is dark gray to black, luster is dull to sub-vitreous, texture is smooth due to water-rolling or tumbling, fine-grained crystal structure.
Formation & geological history
Formed through regional metamorphism of shale or mudstone under moderate heat and pressure over millions of years.
Uses & applications
Used in landscaping, decorative pebbles, tumbling crafts, and sometimes construction.
Geological facts
Dark water-worn pebbles often show distinct fine parallel foliation or ripple marks preserved from ancient sedimentary environments before metamorphism.
Field identification & locations
Commonly found in river beds, beaches, and glacial deposits. Identified by its dark color, fine grain size, and smooth water-worn shape.
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