X-ray diffraction study and luminescence of agates of Southern Siberia

Abstract

Abstract Central part of Kuznetsk Basin is known in the narrow circle of researchers as one of the regions of Siberia where agate mineralization is widespread. In spite of rather wide distribution of these quartz-chalcedony aggregates, still there are some unresolved issues about their origin. In this context it may be informative to use such methods as luminescence analysis and estimation of crystallinity indexes of minerals which constitute agates. Layer-by-layer X-ray diffraction study of minerals which make up distinct layers of agates and onyxes allowed identifying three minerals alternating: chalcedony, quartz and (less frequently) cristobalite. Calculation of crystallinity indexes of all of the layers with use of X-ray diffraction analysis helped to find changes of proportion between two states of silica – high-molecular (polymerized) and monomeric. X-ray luminescence analysis results confirmed this finding. Authors suppose that monomeric state is particularly related to high value of crystallinity index and presence of defects which are responsible for short-wavelength luminescence (280 nm).