It is rich in oxides of magnesium and calcium, but poor in silica. Its namesake flood plains cause the dark ―maria‖  observed on the moon, and formations have been found on Mars and Venus as well as on Earth. Its extrusive form is  called gabbro, and the Punalu‘u Beach in Ha
It is rich in oxides of magnesium and calcium, but poor in silica. Its namesake flood plains cause the dark ―maria‖  observed on the moon, and formations have been found on Mars and Venus as well as on Earth. Its extrusive form is  called gabbro, and the Punalu‘u Beach in Hawaii‘s black sands are made from this material. FTP, name this fine-grained,  black or grey volcanic rock formed by rapid surface cooling of lava.
It is rich in oxides of magnesium and calcium, but poor in silica.