Basalt
From the Simple English Wikipedia, the free encyclopedia that anyone can change
Basalt (IPA: /ˈbæsɒlt, bəˈsɒlt/) is a common gray to black extrusive volcanic rock. It is usually fine-grained because of its rapid cooling of lava manner on the Earth's surface. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria.