Volume 2, Issue 5 (September 1974)
A Spectrophotometric Technique for the Fabric Analysis of Monomineralic Kaolinitic Soils
A technique for identifying the fabric of kaolin clay by measurement of the monochromatic light intensity emanating from the analyzer of a polarizing microscope is described and evaluated analytically and experimentally. This technique is based on the variation of light intensity with the degree of retardation in an optical compensator. Actual fabrics are simulated by super-imposing the optical properties of 2000 individual kaolinite crystals comprising hypothetical fabric models in which the individual c-crystallographic axis directions are normally distributed about a mean direction with respect to the microscope optics. The intensities are computed for models with different mean c-axis directions and degrees of fabric randomness, which is characterized by the standard deviation of the normal distribution, and these intensities serve as a reference to which experimentally obtained intensities for thin sections of kaolinitic soils with unknown fabric are compared. An appreciation of the fabric homogeneity over the area of a thin section can be obtained by use of an equal area spherical projection plot.