Lucien Cayeux (1864-1944) was a crucial scientific figure in France during a particularly hard time in
Europe owing to the two World Wars and the social and economic crisis. His ideas about the relevance of
sediments and sedimentary rocks with regard to both scientific and economic aspects led to him to
recover that the study of ancient sediments would be as much important as that of igneous and metamorphic
rocks, which have been the geology stars by that time. His technical contributions were shaped into three
great marvelously-illustrated monographies devoted to both siliceous, carbonate and ferruginous rocks. In
addition, his main pedagogical output was the valuable atlas for petrographic studies of sedimentary
rocks, which has been the essential reference for all the further didactic texts and atlas on Sedimentary
Petrology