In geology and astronomy, the term silicate is used to mean silicate minerals, ionic solids with silicate anions; as well as rock types that consist predominantly of such minerals. In that context, the term also includes the non-ionic compound silicon dioxide (silica, quartz), which would correspond to in the general formula. The term also includes minerals where aluminium or other tetravalent atoms replace some of the silicon atoms, as in the aluminosilicates. Such silicates comprise most of Earth's crust and mantle, as well as the other terrestrial planets, rocky moons, and asteroids.