EditorialVolcanic bomb. Mass of molten rock (tephra). Formed when a volcano ejects viscous fragments of lava during an eruption. They are extrusive igneous rock. Exemplary from Greece. Natural History Museum, Berlin, Germany.
EditorialGranite. Plutonic igneous rock consisting essentially of quartz, feldspar and mica. Piece from Schneeberg, Germany. Museum fur Naturkunde. Berlin. Germany. Europe.