igneous
Porphyritic Basalt Pebble
Extrusive igneous rock with plagioclase phenocrysts
AI-generated identification · may be incorrectHardness 6 on Mohs scale, reddish-brown weathered exterior, dull to sub-vitreous luster, fine-grained aphanitic matrix with visible lighter phenocrysts, specific gravity around 2.9.
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Physical properties
Hardness 6 on Mohs scale, reddish-brown weathered exterior, dull to sub-vitreous luster, fine-grained aphanitic matrix with visible lighter phenocrysts, specific gravity around 2.9.
Formation & geological history
Formed from rapidly cooling basaltic lava flows exposed to surface weathering and aqueous tumbling over millions of years.
Uses & applications
Used in landscaping, decorative stone, and as a natural worry or skipping stone.
Geological facts
Water tumbling smoothens sharp volcanic edges into smooth pebbles. The reddish hue typically stems from iron oxidation during weathering.
Field identification & locations
Identify by its dense, fine-grained matrix, rounded pebble shape, and weathered reddish-brown exterior. Common in riverbeds and glacial deposits.
