The answer is; Basalt rock
This type of rock is dark-colored due to the high content of magnesium and iron from the lava that forms it. Extrusive basalt rocks are fine-grained due to the rapid cooling of lava on the earth's surface. The basaltic lava is usually of low viscosity to the low silica content. Therefore , this lava flows greater distances before cooling. Basalt comprises approximately 90% of volcanic rocks on earth.
