English: A cut block of trachyandesite lava, used as a type of building stone known locally as "La pierre de Volvic" ("Volvic Stone"), forming part of the walls of Notre-Dame-de-l'Assomption Cathedral in Clermont-Ferrand, France. This rock originally formed part of a trachyandesite lava flow that was erupted 11,000 years ago from Puy de la Nugère volcano during a strombolian-style eruption. This trachyandesite is frost-resistant and has a low coefficient of expansion, making it an attractive material for construction. This view is about 10 centimetres across. (Some parts of this description are based on a translation of some sentences of the French Wikipedia article http://fr.wikipedia.org/wiki/Pierre_de_Volvic which is Copyright CC-BY-SA-3.0).