A thousand plausible and often ingenious theories on the geological character of the diamond have been advanced in modern times or within a century past; and a great variety of rocks or mineral substances extending from itacolumite to xanthophyllite have been affirmed to be the parent mineral. The real matrix, or such as we believe it to be, of the diamond is the same all over the world. The associate minerals which form the conglomerate in which it is generally found may vary somewhat, but the character of the deposit is but little changed. This matrix is a secondary product, and consists of a conglomerate gravel which once abounded in remains of animal and vegetable life. The keen eye of Buffon early detected the formation of the true gem strata; and believing that the gems were produced in these peculiar beds by the solar forces, he boldly asserted that they were formed in the superficial strata from _débris_ of older formations, mineral, animal, and vegetable. “On ne peut leur donner d’autre origine, d’autre matrice que la terre limoneuse qui rassemblant les debris des autres matieres.” This matrix is a well-defined conglomerate, which is found generally on elevated plateaux, and which corresponds to the bottoms of shallow lagoons or lakes of inconsiderable depth. In the earthy portion, which is composed of a variety of _débris_, occur the diamonds, interspersed among the quartz or rock pebbles, and in a marked and continuous layer. These formations are well known to the geologist, for they occur in almost every country on the globe.