Chemical and spectroscopic characterization of some phosphate accessory minerals from pegmatites of the Sowie Góry Mts, SW Poland

Abstract

Aggregates of phosphate accessory minerals from the Michałkowa pegmatite in the Sowie Góry Mts, Lower Silesia, southwestern Poland were studied by means of electron microprobe, IR and Raman spectroscopies. Samples of phosphate minerals were collected from the Michałkowa type locality. Precise chemical analyses in microarea indicate that studied samples are not pure chemical phases, but lamellar intergrowths of various phosphate minerals. These aggregates consist mostly of sarcopside (Fe 2+,Mn 2+,Mg) 3(PO 4) 2 and graftonite (Fe 2+,Mn 2+,Ca) 3(PO 4) 2 with minor amounts of other phosphates. The aims of our study are detailed spectroscopic investigations of sarcopside and graftonite from the Michałkowa site combined with precise chemical analyses. The authors provide a full spectroscopic characterization of these minerals in the ranges from 1400 to 400 cm −1 – IR investigations and from 1300 to 250 cm −1 – Raman investigations. Spectra of pure sarcopside, pure graftonite and mixture of these minerals are compiled. The results show that Raman microspectroscopy allows discerning sarcopside from graftonite in an easy, non-destructive and fast way. Micro-Raman method is proper to distinguish phases in solid solutions as it allows discerning end-members basing on shifted bands in a spectrum. Spectroscopic characterization is also useful in investigation of the presence of H 2O and OH molecules in structure of studied phosphates. Increased content of such molecules can confirm a higher level of phosphate alterations.