OOLITE

is a species of limestone composed of globules clustered together, commonly without any visible cement or base. These vary in size from that of small pin-heads to peas; they sometimes occur in concentric layers, at others they are compact, or radiated from the centre to the circumference; in which case, the oolite is called roogenstein by the German mineralogists. In geology the oolitic series includes all the strata between the iron sand above and the red marl below. It is the great repository of the best architectural materials which the midland and eastern parts of England produce; it is divided into three systems :— 1. The upper oolite , including the argillo-calcareous Purbeck strata, which separate the iron and oolitic series; the oolitic strata of Portland, Tisbury, and Aylesbury; the calcareous sand and concretions, as of Shot over and Thame; and the argillo-calcareous formation of Kim me ridge, the oak tree of Smith. 2. The middle oolite ; the oolitic strata a ociated with the coral rag; calcareous sand and grit; great Oxford clay, between the oolites of this and the following system. 3. The lower oolite ; which contains numerous oolitic strata, occasionally subdivided by thin argillaceous beds; including the cornbrash, forest marble, schistose oolite, and sand of Stones field and Hinton, great oolite and inferior oolite; calcareo-siliceous sand pa ing into the inferior oolite; great argillo-calcareous formation of lias, and lias marl, constituting the base of the whole series. These formations occupy a zone 30 miles broad in England.