Structural studies of new zealand pounamu using mössbauer spectroscopy and electron paramagnetic resonance

Abstract

We report Mössbauer spectroscopy and electron paramagnetic resonance spectroscopy (EPR) studies of a number of New Zealand minerals that can be classified under the non‐specific names “pounamu” or “greenstone”. Mössbauer measurements allowed the distribution of iron in its +2 and +3 oxidation states to be assigned to the M1 to M4 sites of the constituent minerals, tremolite‐actinolite in the case of nephrite jades. EPR at two frequencies, 9.4 GHz (X‐band) and 94.1 GHz (W‐band), allowed the determination of the distribution of Mn2+ in these sites. The results are apparently contrary to the usual assignments made for the parent minerals tremolite and actinolite. In two cases, one a nephrite jade and the other a serpentine, significant quantities of magnetically ordered minerals chalcopyrite and magnetite were identified by Mössbauer spectroscopy. These minerals could not be found in the X‐ray diffraction patterns of the same minerals leading to the conclusion that they are very finely divided in the samples studied. © 2005 Taylor & Francis Group, Ltd.