ABSTRACT

The mutual disposition of mineral particles and voids in the micron and sub-micron size ranges is generally inaccessible to observation by light microscopy. This instrumental limitation can be overcome by the use of an electron optical system. The scanning electron microscope is an ideal tool for this kind of work, for it produces good resolution at high magnifications with relatively enormous depth of focus. Micrographs obtained with a scanning electron microscope are used to illustrate the fabrics of some fine-grained limestones and clay soils which have properties of special engineering interest. Fine structure is revealed with unusual clarity. Of particular interest are: the nature of contacts of fine-grained crystals with one another and with coarser crystals, particularly dolomi es; the disposition of non-carbonates and (or) cementitious material along grain boundaries; and the orientation of mica-type minerals in shales, mudstones, and clay soils. The relative merit of several methods of sample preparation is discussed.