igneous
Likely basaltic rock
Basalt, a fine-grained mafic volcanic rock composed chiefly of plagioclase feldspar, pyroxene, and commonly olivine
AI-generated identification · may be incorrectDark gray to black, dull to weakly glassy, with a fine-grained crystalline texture; Mohs hardness about 5–6, poor or indistinct cleavage, and specific gravity roughly 2.8–3.0. The specimen appears weathered and may include lighter alteration minerals.
Identified More igneous →
Explore Likely basaltic rock in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray to black, dull to weakly glassy, with a fine-grained crystalline texture; Mohs hardness about 5–6, poor or indistinct cleavage, and specific gravity roughly 2.8–3.0. The specimen appears weathered and may include lighter alteration minerals.
Formation & geological history
Basalt forms when low-silica magma rapidly cools at or near Earth’s surface, commonly in lava flows, oceanic crust, and volcanic islands. Individual specimens may range from recent volcanic material to Precambrian age.
Uses & applications
Used extensively as crushed aggregate, road base, railway ballast, riprap, and dimension stone; attractive polished basalt is used decoratively. Ordinary hand specimens generally have little commercial value.
Geological facts
Its dark color reflects abundant iron- and magnesium-rich minerals. Vesicles, if present, may later fill with zeolite, calcite, or quartz, producing amygdaloidal basalt.
Field identification & locations
Common worldwide, especially in Hawaii, Iceland, India’s Deccan Traps, the Columbia River region, and oceanic crust. Identification is supported by dark color, fine texture, heavy feel, and lack of visible large crystals; the image alone cannot exclude fine-grained andesite or weathered gabbro.
