A mineral with the idealised composition ZrSiO₄, one of the chief sources of the element zirconium. Trace amounts of uranium and of thorium are often present and the mineral may then be partly or entirely metamict. The name cyrtolite is applied to an altered type of zircon. Structurally, zircon is a nesosilicate, with isolated SiO₄ groups. It is isostructural with the thorium silicate thorite and the yttrium phosphate xenotime.