igneous
Basalt (likely vesicular basalt)
Basalt; chiefly plagioclase feldspar, pyroxene, and often olivine
AI-generated identification · may be incorrectDark gray to black, fine-grained, dull to mildly vitreous, with an irregular possibly vesicular surface; hardness about 5–6 Mohs, generally massive with no obvious cleavage. The image is insufficient to confirm mineral grains or vesicles.
Identified More igneous →
Explore Basalt (likely vesicular basalt) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray to black, fine-grained, dull to mildly vitreous, with an irregular possibly vesicular surface; hardness about 5–6 Mohs, generally massive with no obvious cleavage. The image is insufficient to confirm mineral grains or vesicles.
Formation & geological history
An extrusive igneous rock formed when mafic lava rapidly cooled at or near Earth’s surface, commonly from Cenozoic to Recent volcanic activity. Typical settings include lava flows, volcanic islands, and mid-ocean ridges.
Uses & applications
Used as crushed aggregate, road base, riprap, concrete aggregate, and building stone; attractive polished varieties are used decoratively.
Geological facts
Basalt is the most abundant volcanic rock on Earth and forms much of the oceanic crust. Magnetic basalt may contain iron oxides such as magnetite.
Field identification & locations
Identify it by its heavy, dark, fine-grained appearance and lack of visible quartz; a streak, hardness, density, and fresh broken surface help distinguish it from slag or weathered iron-rich rock. Common worldwide in volcanic regions.
