The Moon probably also condensed out of the swirling gases as a separate mini-planet. This was captured by the gravitational pull of Earth and became our Moon. Before we finally landed robots and eventually humans on the Moon in the 1960s we were unsure of its composition. Lunar samples which were brought back show that it is a volcanic rock similar to many of the volcanic rocks on Earth. Most of the Moon is made of a volcanic rock called basalt.
Basalts form on Earth when volcanos erupt throwing out molten rocks into the air or the sea.
Basalts are made of four main elements. They are mainly silicon, but they also contain iron, aluminium and magnesium. Silicon is the most abundant element on the Earth and occurs in many rocks. Sand on a beach is largely silicon. Iron, aluminium and magnesium are all metals that occur in rocks on Earth as well and are used to make things as diverse as cars and drinks cans.