Textures and Microstructures

Abstract

Texture has already been defined (p. 33) as the intimate mutual relations of the mineral constituents and glassy matter in a rock made up of a uniform aggregate. It is best studied in thin section under the microscope. Microstructures, also studied in the same way, are due to the juxtaposition of two or more kinds of textural aggregates in a rock. Textures and structures are important, as these features are the indices of the geological processes which have been in operation; and their study provides valuable information as to the physical chemistry of the cooling and solidification of igneous rocks.

A. Holmes, Petrographic Methods and Calculations, 1921, Chap. IX; J. P. Iddings, Igneous Rocks, vol. i, 1909, Chap. VI; A. Harker, Natural History of Igneous Rocks, 1909, Chap. XI. For the arrangement of this chapter I am especially indebted to Holmes.