BRECCIA, brecha, connected with breach and break, a conglomerate composed of angular pieces of the same or of different rocks, united by a cement or matrix, which, according to its nature, forms the several varieties of calcareous, silicious, etc. The cementing material may consist of calcite, iron oxide, quartz or various kinds of clay. The conglomerate known by the name of pudding-stone differs from that of breccia only in having the composing frag ments rounded. Calcareous breccia is often found in the form of fine marble, apparently composed of fragments produced by some dis rupting force, and then united by the infiltra tion of carbonate of lime among them. The angular form of the fragments seems to indicate that they have never been exposed to much fric tion, and have therefore probably originated at no great distance from their present site. In some cases a kind of spurious breccia has been formed by the breaking up of calcareous beds, and their subsequent union by means of infil tration, without any change of their original position. Marble breccia thus formed is re
markable for the size of its fragments. In the calcareous districts of many countries caverns and extensive fissures are seen filled with a red dish mass, composed of lime, sand and oxide of iron, enclosing angular fragments of different rocks, and a great number of bones more or less broken. To such masses the name of os seous breccia has been given. They are most frequently met with on the shores of the Medi terranean. Brecchia is formed by the breaking of rock into angular fragments by dynamic action and cementation; by angular blocks thrown from volcanoes and afterward consoli dated; by a process similar to that of conglom erate; by the hardening and breaking into fragments of the surface of a lava flow and its subsequent burial in the soft magma; by the cementation of the loose fragment, always angular in form, of screes or talus slopes; by fragments broken from the walls of intruding igneous rocks and caught in the molten mass.