Complex sentence: Unusually, mullite has no charge balancing cations present therefore there are three different Al sites: two distorted tetrahedral Al sites and one Al other site which adopts a higher co-ordinate octahedral state.
Split into simpler sentences: Unusually, mullite has no charge balancing cations present. As a result there are three different Al sites: two distorted tetrahedral Al sites and one Al other site which adopts a higher co-ordinate octahedral state.