What is the oxidation state of Cu and Fe in chalcopyrite ($\ce{CuFeS2}$)? Some websites tell that it is $\ce{Cu(I)Fe(III)S2}$, and others tell that it is $\ce{Cu(II)Fe(II)S2}$. Which is right?


A number of papers report that the formal valency states of chalcopyrite are best considered as $\ce{Cu+Fe^3+S2}$, based on various computational and spectroscopic evidence.


  1. Klekovkina, V. V.; Gainov, R. R.; Vagizov, F. G.; Dooglav, A. V.; Golovanevskiy, V. A.; Pen’kov, I. N. Oxidation and magnetic states of chalcopyrite CuFeS2: A first principles calculation. Opt. Spectrosc. 2014, 116 (6), 885–888. DOI: 10.1134/S0030400X14060149.

  2. Pearce, C.; Pattrick, R.; Vaughan, D.; Henderson, C.; van der laan, G. Copper oxidation state in chalcopyrite: Mixed Cu d9 and d10 characteristics. Geochim. Cosmochim. Acta 2006, 70 (18), 4635–4642. DOI: 10.1016/j.gca.2006.05.017.

  3. Goh, S. W.; Buckley, A. N.; Lamb, R. N.; Rosenberg, R. A.; Moran, D. The oxidation states of copper and iron in mineral sulfides, and the oxides formed on initial exposure of chalcopyrite and bornite to air. Geochim. Cosmochim. Acta 2006, 70 (9), 2210–2228. DOI: 10.1016/j.gca.2006.02.007.

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