igneous
Basalt Pebble
Extrusive mafic igneous rock
Hardness 6 on Mohs scale, dark grey to black/brownish earthy color, dull to sub-vitreous luster, fine-grained aphantic microcrystalline structure, poor cleavage, high specific gravity (approx. 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 6 on Mohs scale, dark grey to black/brownish earthy color, dull to sub-vitreous luster, fine-grained aphantic microcrystalline structure, poor cleavage, high specific gravity (approx. 2.8 - 3.0).
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich basaltic lava at or near the Earth's surface. Water-worn and rounded through mechanical weathering in river beds or ocean coasts.
Uses & applications
Used as construction aggregate, road base, river rock landscaping, railroad ballast, and in stone carving or lapidary tumbling.
Geological facts
Basalt is the most common rock type in the Earth's crust, forming almost all of the oceanic crust. It is also found extensively on the Moon and Mars.
Field identification & locations
Identified by its fine grain size, dark color, heaviness, and smooth, rounded surface from natural erosion. Common near rivers, lakes, beaches, and volcanic landscapes worldwide.
