Cordite

Cordite is a material that is strong that can only be destroyed using the Super Missile. Its first appearance was in Metroid Prime. It appeared in the Sun Tower in the Chozo Ruins and other places. If you broke it, you could get one lock. If you broke the other one, you could get the second lock. It has a weird shape in Metroid Prime. It has a circle and other little things around it. It also appears in Metroid Prime 2: Echoes as the Super Missile door.