Zircon is very durable. It is hard and has a high melting point of around2,500 °C (4,530 °F). Therefore it has survived for a very long time, even throughmetamorphic very warm processes deep underground, which otherwise melts or converts normal rocks.
Zircons from theJack Hills in the NarryerGneiss Terrane,Yilgarn Craton,Western Australia, have yielded U–Pb (uranium–leadradioactive dating) ages up to 4.404 billion years.[1] This is judged to be the age ofcrystallization, making them the oldest minerals so far dated on Earth. In addition, theoxygenisotopic compositions of some of these zircons indicate that more than 4.4 billion years ago there was already water on the surface of the Earth.[1][2] This interpretation is supported by additional trace element data,[3][4] but is also the subject of debate.[5][6]
