Original: A common empirical formula showing some of the range of substitution in zircon is ( Zr1 -- y , REEy ) ( SiO4 ) 1 -- x ( OH ) 4x -- y. Zircon forms in silicate melts with concentrated incompatible elements and accepts high field strength elements into its structure .
Simplified: In addition , the oxygen isotopic 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 .