Contribution to the crystallography of hydrotalcites: the crystal structures of woodallite and takovite

The crystal structures of the 3R polytypes of takovite and woodallite are presented. The structure of takovite was solved on a single crystal from the Agoudal mine, Bou Azzer district, Tazenakht, Morocco to R1 = 1.87 % for 94 unique reflections [Fo>4σF] in R-3m, with unit cell parameters a = 3.0290(2) and c = 22.5995(15) . The crystal structure of woodallite [space group R-3m, with unit cell parameters a = 3.10124(8) and c = 23.6817(16) ] was refined utilising the Rietveld method on a sample from the MKD5 orebody at the Mount Keith Nickel Mine, Western Australia.