- GeoRef, Copyright 2006, American Geological Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States
The individual clay mineral particles that compose clayey sediments are usually too small to permit their optical properties to be determined. A technique is described for obtaining aggregates of clay mineral particles in which all the individual particles have about the same optical orientation so that the optical constants of the clay mineral can be measured easily and accurately. The problem presented by fine calcite, which masks the optical constants of the clay mineral and of which the removal is difficult without altering the clay mineral, is met by an improved method for eliminating fine calcite from calcareous sediments.