igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, dark gray to black color, dull to sub-metamorphic luster, aphanitic (fine-grained) crystal structure, no prominent cleavage, specific gravity around 2.8-3.0.
Identified More igneous →
Explore Basalt Pebble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, dull to sub-metamorphic luster, aphanitic (fine-grained) crystal structure, no prominent cleavage, specific gravity around 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava exposed at or very near the surface of a planet or moon. Geological age varies widely from recent volcanic eruptions to billions of years old.
Uses & applications
Used widely in construction as crushed aggregate for roads, railroad ballast, concrete production, and sometimes as dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins and also makes up extensive volcanic formations on the Moon and Mars.
Field identification & locations
Can be identified in the field by its dark, fine-grained appearance, heavy feel due to iron and magnesium content, and occurrence in volcanic regions or water-worn riverbeds and beaches.
