The material examined was obtained from a Gallo-Roman dwelling of the 3rd-4th century in the canton of Laon, Aisne, France. On granulometric and chemical analyses, it was found to be an alluvial calcareous sand and was described as a chalk mortar. Microscopic examination of a sample revealed an almost even distribution of quartz grains in fine chalk in the approximate ratio of 30:70 by volume. Smaller quantities of flint, baked clay particles and clay were also detected. It could not be decided whether the material formed part of a wall or a floor. -- AATA