igneous
Rounded dark pebble, likely basalt
Basalt (probable; identification is uncertain from the photo)
AI-generated identification · may be incorrectFine-grained, dark gray-brown and rounded by abrasion, with a dull to weakly glassy surface. Basalt is typically Mohs 5–6, composed mainly of plagioclase and pyroxene, with no visible cleavage; this pebble’s exact composition cannot be confirmed visually.
Identified More igneous →
Explore Rounded dark pebble, likely basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Fine-grained, dark gray-brown and rounded by abrasion, with a dull to weakly glassy surface. Basalt is typically Mohs 5–6, composed mainly of plagioclase and pyroxene, with no visible cleavage; this pebble’s exact composition cannot be confirmed visually.
Formation & geological history
If basalt, it formed when iron- and magnesium-rich lava cooled quickly at or near the surface; basalt ranges from recent to billions of years old. The rounded shape suggests prolonged transport or tumbling in water or sediment.
Uses & applications
Commonly used as crushed aggregate, road stone, and landscaping material; this small pebble has little commercial value but may be kept as a natural specimen.
Geological facts
The pale mark may be a mineral-filled cavity or a surface chip, but the image does not establish which.
Field identification & locations
Its compact, dark, fine-grained appearance is consistent with basalt, though other dark rocks are possible. A hardness test and fresh broken surface would help identify it; common sources include volcanic regions and river or beach gravels.
