PHYSICAL METHODS OF IDENTIFICATION OF THE FELDSPARS FROM GRANITIC PEGMATITES ê

The mineral samples analysed in this paper are K, Na, Ca aluminosilicates known as feldspars and belong to the granitic pegmatites developed in the ConţuNegovanu area, in the Southern Carpathians (Romania). Some of the samples were subjected to X-ray powder diffraction analysis and the obtained data enabled the identification of the precise feldspar terms, as well as some of their structural characteristics. The determined refractive indices and the respective birefringence data, interferometrically determined for yellow Na radiation were plotted on a determinative chart, confirming the previous determined chemical composition of the feldspar terms. The IR spectra also display characteristic features of the determined feldspar terms.