The Physical Origin of Certain Concretions

Abstract

The literature on the subject of concretions is somewhat limited in extent, and consists largely of descriptive rather than theoretical matter. It is safe to say, however, that distinct types present different problems for solution, and have resulted from divers combinations of chemical and physical laws. The forces brought to play in the forming of one kind may have played no part in the creation of another. Types vary to such a degree that a valid classification is difficult to prepare. Certain writers have made general classifications with reference to manner of growth; for instance, Dana2 employs the terms "centrifugal" and "centripetal" concretions for growths to and from a center respectively. The latter includes principally concretions of a geodal character. In a similar way the terms "excretions" and "incretions" have been used.3