igneous
Black Pebble (Basalt / Chert)
SiO2 (if Chert) or Mafic Igneous Rock (if Basalt)
Hardness 6-7 on Mohs scale, deep dark brown to black color, smooth waxy or satin luster from natural river or beach erosion, microcrystalline or fine-grained texture
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Physical properties
Hardness 6-7 on Mohs scale, deep dark brown to black color, smooth waxy or satin luster from natural river or beach erosion, microcrystalline or fine-grained texture
Formation & geological history
Formed either through volcanic cooling of mafic lava (basalt) or sedimentary precipitation of microcrystalline quartz (chert), naturally rounded and polished by water abrasion over time
Uses & applications
Used in landscaping, decorative stone collections, aquariums, hot stone massage therapy, and tactile stress relief stones
Geological facts
Water-worn pebbles get their smooth, aerodynamic teardrop shapes from millions of tumbling actions against sand and other stones in riverbeds or ocean surf.
Field identification & locations
Look for a smooth, featureless dark surface that does not scratch easily with a steel nail. Commonly found along stream beds, river channels, ocean beaches, and alluvial deposits.
