Mg K-edge XANES of sepiolite and palygorskite

a £SRF, BP 220 F-38043 Grenoble Cedex, France b Dpto, Geologia, Universidad de Salamanca, £-37008 Salamanca, Spain C Dpto. Cristalogra/ia y Mineralogia, U Complutense de Madrid, £-28040 Madrid, Spain d INFM, clo £SRF, BP 220 F-38043 Grenoble Cedex, France e Lab. Cristallographie, CN RS, Grenoble BP 166, F-38042 Grenoble Cedex 09, France f INAH, Mexico DF, Mexico g TASC-INFM Area Science Park, 1-34012 Trieste, Italy We present a study of the Mg K-edge on sepiolite and palygorskite performed at the INFM BEAR beamline at Elet­ tra synchrotron light source (Trieste). These two clays, although having very similar structures, show some different features in their near-edge. Mg is in octahedral coordination with oxygens, hydroxyl groups or water, for both paly­ gorskite and sepiolite. The differences found in the near-edge seem to reflect the fact that, on average, an Mg atom in palygorskite "sees" less Mg in higher coordination shells than sepiolite.