Hydrous Silicates Injecting the Pores of Fossils

Abstract

DR. T. STERRY HUNT directed attention some time ago* to a remarkable limestone of Silurian age from Pole Hill, New Brunswick, in which I had found the cavities of fossil crinoids to be filled with a siliceous substance perfectly injecting their most delicate cellular structure, and which Dr. Hunt, on chemical analysis, found to be a hydrous silicate allied to jollyte. I have since, in examining with the microscope various specimens of limestone in the collection of McGill College, met with a British example of this kind of injection, to which I would wish to direct the attention of your microscopists. It is a specimen of olivaceous, imperfectly crystalline limestone, labelled Llangedoc, Wales. The only distinct fossil which it contains is a small body having the characters of the genus Verticillopora. It is filled, however, with crinoidal fragments and fragments of shells, and, when sliced, displays a few very minute univalves, probably of the genus Murchisonia, and also portions of a sponge-like organism with square meshes. The pores and cavities of many of these fossils are filled with a greenish or brownish finely crystalline silicate, which must have been introduced when the organic bodies were still recent, and which Dr. Hunt has ascertained to have the following composition:—