Vibrational spectroscopic study of the phosphate mineral kryzhanovskite and in comparison with reddingite-implications for the molecular structure.

Abstract

We have studied the phosphate mineral kryzhanovskite (Fe3þ,Mn2þ)3(PO4)2(OH,H2O) which is a member of the phosphoferrite mineral group using a combination of scanning electron microscopy with energy dispersive spectroscopy and Raman and infrared spectroscopy. Chemical analysis shows the presence of P, Mn and Fe and confirms the formula given above. The presence of hydroxyl units in the structure is indicative of ferric iron in the formula that is an oxidised product. Raman spectroscopy coupled with infrared spectroscopy supports the concept of phosphate, hydrogen phosphate and dihydrogen phosphate units in the structure of kryzhanovskite -phosphoferrite. Infrared and Raman bands attributed to water and hydroxyl stretching modes are identified. Vibrational spectroscopy adds useful information to the molecular structure of kryzhanovskite -phosphoferrite.