The igneous rock that forms when basaltic lava hardens is basalt. Basalt is the most common type of extrusive igneous rock, meaning it usually forms from lava flows as opposed to being formed from magma deep within the earth.
Much of the oceanic crust is made of basalt made from the lava flows of submarine volcanoes. Basalt is usually a very dark gray to black rock with a fine grain.
Spilite is rock that forms from the cooling of basaltic lava that has interacted with seawater. Spilite differs from basalt in that it contains albite, chlorite and calcite and may be veined with chalcedony, a type of quartz.