The phosphate mineral arrojadite-(KFe) and its spectroscopic characterization.

Abstract

The arrojadite- (KFe)mineral has been analyzed using acombination of scanning electron microscopy and a combination of Raman and infrared spectroscopy. The origin of the mineral is Rapid Creek sedimentary phosphatic iron formation ,northern Yukon. The formula of the mineral was determined as K2:06Na2Ca0:89Na3:23ðFe7:82Mg4:40Mn0:78ÞR13:00Al1:44ðPO4Þ10:85ðPO3OH0:23ÞðOHÞ2. The complexity of the mineral formula is reflectedin the spectroscopy. Raman bands at 975, 991 and 1005 cm _1 with shoulder bands at 951 and 1024 cm _1 are assigned to the PO 3_ 4 m1 symmetric stretching modes. The Raman bands at 1024, 1066, 1092, 1123, 1148 and 1187 cm _1 are assigned to the PO 3_ 4 m3 antisymmetric stretching modes. Aseries of Raman bands observed at 540, 548, 557, 583, 604, 615 and 638 cm _1 are attributed to the m4 out of plane bending modes of the PO 4 and H2PO4 units. The m2 PO4 and H2PO4 ben ding modes are observed at 403, 424, 449, 463, 479 and 513 cm _1. Hydroxyl and water stretching bands are readily observed. Vibrational spectroscopy enables new information about the com- plex phos phate mineral arrojadite-(KFe)to be obtained.