Zircon crystals, 4.1 billion years old, found at Mount Narrayer, Western Australia. Dated by the decay of their uranium content as being older than 4.1 billion years these are among the oldest fragments of Earthly material ever found. Australia alone has material of this age and it all comes from a thin strip of primordial crust (the Western Gneiss Terrain) that runs down beside the western edge of Western Australia from Mount Narryer, to beyond Greenbushes in the south-west corner of the State.