igneous
Basalt River Stone
Aphanitic Mafic Igneous Rock
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/Sub-metallic when wet, Crystal Structure: Microcrystalline (aphanitic), Specific Gravity: 2.8–3.0
Identified More igneous →
Explore Basalt River Stone in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/Sub-metallic when wet, Crystal Structure: Microcrystalline (aphanitic), Specific Gravity: 2.8–3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This specific specimen has been Rounded by fluvial (river) erosion over many years.
Uses & applications
Commonly used in construction as aggregate, for stone walls, and sometimes in landscaping or as aquarium decor. Tumbled versions are used in massage therapy (hot stones).
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found extensively on the Moon and Mars.
Field identification & locations
Identified by its dark color, heavy weight (density), and fine-grained texture. Large deposits are found in the Pacific Northwest (Columbia River Basalt Group) and various volcanic regions.
