Analysis of weathering products formed on Saxonean Cretaceous sandstones

Abstract

The most obvious appearance of weathering on Saxonean Cretaceous sandstones is the formation of black layers on the surface. The origin of these layers may be increased atmospheric pollution, different climatic conditions, the sandstone itself and the activity of micro-organisms. Various techniques, particularly infrared spectroscopy, X-ray diffraction and Mössbauer spectroscopy, were used to identify accessory minerals in the bulk of different sandstones and to investigate the nature of the weathering products on the surfaces. Salt-like components present are predominantly gypsum. Different iron oxides such as hematite, maghemite and magnetite are involved in the formation of the black layers and explain their dark colour to some extent. The exposure to rain and sunshine has an important influence on the selection or formation of various iron minerals. The main source of the iron is the interior of the sandstone.