Zircon

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Zircon crystal from Brazil.

Zircon is a silicate mineral. It is found in many different places in almost all kinds of rock. The chemical it is made up of is called zirconium silicate: ZrSiO4. Clear zircon may look like diamond and has been used as a cheaper replacement for diamond. It is not the same as cubic zirconia, which is man-made from different chemicals. In the United States, zircon is considered to be the birth stone for the month of December.

Long lasting zircons[change | edit source]

Zircons from the Jack Hills in the Narryer Gneiss Terrane, Yilgarn Craton, Western Australia, have yielded U–Pb (uranium–lead radioactive dating) ages up to 4.404 billion years.[1] This is judged to be the age of crystallization, making them the oldest minerals so far dated on Earth. 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.[1][2] This interpretation is supported by additional trace element data,[3][4] but is also the subject of debate.[5][6]

References[change | edit source]

  1. 1.0 1.1 Wilde S.A., Valley J.W., Peck W.H. and Graham C.M. (2001). "Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago". Nature 409: 175. doi:10.1038/35051550. http://www.geology.wisc.edu/%7Evalley/zircons/Wilde2001Nature.pdf.
  2. Mojzsis, S.J., Harrison, T.M., Pidgeon, R.T. (2001). "Oxygen-isotope evidence from ancient zircons for liquid water at the Earth’s surface 4300 Myr ago". Nature 409: 178–181. doi:10.1038/35051557.
  3. Ushikubo, T., Kita, N.T., Cavosie, A.J., Wilde, S.A. Rudnick, R.L. and Valley, J.W. (2008). "Lithium in Jack Hills zircons: Evidence for extensive weathering of Earth's earliest crust". Earth and Planetary Science Letters 272: 666–676. doi:10.1016/j.epsl.2008.05.032.
  4. "Ancient mineral shows early Earth climate tough on continents". Physorg.com. June 13, 2008. http://www.physorg.com/news132583481.html.
  5. Nemchin, A.A., Pidgeon, R.T., Whitehouse, M.J. (2006). "Re-evaluation of the origin and evolution of >4.2 Ga zircons from the Jack Hills metasedimentary rocks". Earth and Planetary Science Letters 244: 218–233. doi:10.1016/j.epsl.2006.01.054.
  6. Cavosie, A.J., Valley, J.W., Wilde, S.A., E.I.M.F. (2005). "Magmatic δ18O in 4400–3900 Ma detrital zircons: a record of the alteration and recycling of crust in the Early Archean". Earth and Planetary Science Letters 235: 663–681. doi:10.1016/j.epsl.2005.04.028.