Solidified lava is also known as BASALT, which is a type of igneous rock formed from the rapid cooling of lava. BASALT is a dark-colored, fine-grained, igneous rock composed mainly of plagioclase and pyroxene minerals. It is most commonly formed as an extrusive rock, such as a lava flow, but can also form as an intrusive rock, such as a dike or a sill. BASALT has a low silica content, making it denser than other types of rocks. It is also very strong and resistant to weathering and erosion.