Basalt, close-up. This black volcanic rock has formed from the solidification of a lava flow. It contains microscopic crystals of the minerals plagioclase, pyroxene and green olivine. The lava formed by partial melting of the mantle at a depth of about 80 kilometres. This specimen is from the Upper Miocene (9.5 million years ago). It is part of the Geoscope geological park, located between Les Monts-Vert and Albaret-Sainte-Marie, central France.