Red sandstone, close-up. This detrital sedimentary rock sample contains quartz and feldspar grains and some white mica. The argillaceous (clay-containing) cement-like bulk of the rock is coloured by iron oxide. This specimen dates from the Eocene (37 million years ago), and formed on the bottom of a lake. It is used as a construction stone. This specimen is part of the Geoscope geological park, located between Les Monts-Vert and Albaret-Sainte-Marie, central France.