Mg K-edge XANES of sepiolite and palygorskite

We present a study of the Mg K-edge on sepiolite and palygorskite performed at the INFM BEAR beamline at Elettra 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 palygorskite 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.