igneous
Polished basalt pebble
Basalt, primarily plagioclase feldspar, pyroxene, and iron-titanium oxides
AI-generated identification · may be incorrectDark gray-black, fine-grained, locally vesicular, with a glassy-to-dull polished luster and orange-brown weathering or alteration patches. Hardness is about 5–6 Mohs; cleavage is not apparent and specific gravity is roughly 2.8–3.0.
Identified More igneous →
Explore Polished basalt pebble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray-black, fine-grained, locally vesicular, with a glassy-to-dull polished luster and orange-brown weathering or alteration patches. Hardness is about 5–6 Mohs; cleavage is not apparent and specific gravity is roughly 2.8–3.0.
Formation & geological history
Basalt is an extrusive volcanic rock formed when mafic lava rapidly cooled at or near Earth’s surface, commonly in oceanic crust and volcanic fields. The specimen is likely geologically ancient relative to its collection context, but its age cannot be determined from the image.
Uses & applications
Used as crushed aggregate, road stone, dimension stone, landscaping material, and occasionally as a decorative polished pebble.
Geological facts
The rounded shape indicates transport and abrasion by water, ice, or sediment. Orange-brown areas may represent iron-oxide staining, while small cavities are former gas bubbles.
Field identification & locations
Identify it by its heavy, dark, fine-grained appearance, lack of visible large crystals, and possible magnetic response from iron oxides or magnetite. Common sources include volcanic terrains and river or beach gravels worldwide.
