On some Occurrences of Spherulitic Siderite and other Carbonates in Sediments

Publisher Website
Google Scholar
Abstract
I. Introduction, and Summary of Earlier Work Mineral crystallizations possessing a radiate or divergent form are of common occurrence in certain types of igneous rocks, and to a more limited extent in sedimentary rocks. In igneous rocks these structures were first examined and described by H. Vogelsang (1), who gave to them the name of ‘spherulitic structures’, a term which has since been employed by petrologists for these igneous rock-growths in particular and for similar structures in general. J. P. Iddings (2), in 1891, in a review of these igneous spherulites, pointed out that their essential feature was crystallization outwards from a centre or from a number of neighbouring centres, with a divergent or radiate arrangement, and that any concentric zoning or banding present was incidental to the radiate growth, since such bands or zones become truncated at points of contact with an obstacle, or with an adjacent spherulite. Dr. Alfred Harker (3), in his ‘Natural History of Igneous Kocks’, discussed these igneous structures, and suggested that they had been formed by relatively rapid crystallization from saturated or supersaturated solutions. In sedimentary rocks, spherulitic structures occur sometimes in the form of large isolated individuals, and sometimes as colonies of small interfering units. The latter variety which, on the one hand, possesses many of the features of igneous spherulites, appears to pass gradually, on the other hand, by an increase in the amount of zoning or banding, into true oolitic structures. Modern research in colloid chemistry has brought new facts to

This publication has 11 references indexed in Scilit: