We propose to use POLARIS to perform two related experiments. Firstly we will investigate the structures and compositions of derivatives of some layered Mn/Cu oxysulfides which have been obtained by oxidative deintercalation of Cu from the sulfide layers using iodine. Secondly we will compare some of these with related copper-deficient samples obtained by electrochemical methods. This accompanies a companion experiment on OSIRIS which will enable the magnetic structures of these materials to be determined and correlated with compositions and structures.