Title: Phosphate minerals from Albian phosphorites in Bulgaria
Abstract:Results from X-ray diffraction analyses of Albian phosphorites from deposits Sanadinovo, Dekoy and Brushlen indicate presence mainly of fluorapatite and partly of chlorapatite and carbonate fluorapati...Results from X-ray diffraction analyses of Albian phosphorites from deposits Sanadinovo, Dekoy and Brushlen indicate presence mainly of fluorapatite and partly of chlorapatite and carbonate fluorapatite (francolite). The microprobe analyses of phosphate grains, coatings, cements, ammonite, wood, and shark tooth determined the following contents (in weight %): 26,65-41,02 P2O5 45,19-57,17 CaO, 2,58-4,64 F, up to 0,80 CI, and silicate components from the admixtures in phosphate minerals. Fifteen crystallochemical formulae were calculated. They are characteristic with Ca9.54-9.58[PO4]5.77-5.78FI1.48-2.81 and Cl0.06-0.30. Generally fluorapaiIte was determimid in 9 samples; and chlorine containing fluorapatite - in 6 samples. The exemplary crystallochemical formulae are: Ca9.54[PO4]5.78F2.75 - fluorapatite Ca9.58[PO4]5.77F1.94CI0.30 - chlorine containing fluorapatite The presence of CO3- and OH in the phosphate minerals was not substantiated by direct data. The studied phosphate minerals show high solubility in lemon acid (30-80%). This indicates defects in the crystal lattices caused by the presence of chlorine and most probably of carbonate group.Read More