Raman spectroscopy of the multi-anion mineral schlossmacherite (H3O,Ca)Al3(AsO4,PO4,SO4)2(OH)6

The mineral schlossmacherite (H 3 O,Ca)Al 3 (AsO 4 ,PO 4 ,SO 4 ) 2 (OH) 6 , a multi-cation–multi-anion mineral of the beudantite mineral subgroup has been characterised by Raman spectroscopy. The mineral and related minerals functions as a heavy metal collector and is often amorphous or poorly crystalline, such that XRD identification is difficult. The Raman spectra are dominated by an intense band at 864 cm −1 , assigned to the symmetric stretching mode of the AsO 4 3− anion. Raman bands at 809 and 819 cm −1 are assigned to the antisymmetric stretching mode of AsO 4 3− . The sulphate anion is characterised by bands at 1000 cm −1 ( ν 1 ), and at 1031, 1082 and 1139 cm −1 ( ν 3 ). Two sets of bands in the OH stretching region are observed: firstly between 2800 and 3000 cm −1 with bands observed at 2850, 2868, 2918 cm −1 and secondly between 3300 and 3600 with bands observed at 3363, 3382, 3410, 3449 and 3537 cm −1 . These bands enabled the calculation of hydrogen bond distances and show a wide range of H-bond distances.