igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale; typically dark grey to black in color; dull to submetallic luster; fine-grained (aphanitic) crystal structure with microscopic minerals; specific gravity around 2.8 to 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; typically dark grey to black in color; dull to submetallic luster; fine-grained (aphanitic) crystal structure with microscopic minerals; specific gravity around 2.8 to 3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in iron and magnesium exposed at or very near the surface of a planet or moon.
Uses & applications
Used extensively in construction as crushed aggregate for roads, railroad ballast, concrete production, and sometimes cut into tiles or monuments.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins, and it is also abundantly found on the Moon and Mars.
Field identification & locations
Found in riverbeds, beaches, and glacial deposits worldwide where water and weathering have smoothed igneous outcroppings into pebbles. Identify by its dense, dark, fine-grained appearance.
