ABSTRACT
The physical properties of sediments depend on a number of factors, including composition, texture, and structure of the original formation; topography; type of weathering; and sorting (Lobeck, 1939). The greatest variety of minerals and textures in sediment comes from the weathering of igneous rocks, especially from this disintegration in semiarid and arid climates. These conditions have produced great volumes of sediment containing much coarse material, including boulders, especially along mountain fronts and in intermountain valleys. These deposits commonly contain a relatively high proportion of unaltered minerals such as feldspars, amphiboles, pyroxenes, and micas. Sediments produced by erosion in more humid and deeply weathered areas generally have a finer texture and a higher proportion of minerals produced by chemical weathering. Some small grains of certain minerals, classified as detrital mineral suites, are resistant to chemical weathering. These include zircon, quartz, rutile (titanium oxide), tourmaline, topaz, and ilmenite (titanium-iron oxide); they remain in sediment relatively unchanged and may reveal the source rock type (Krumbein and Sloss, 1963). Feldspars, the most common minerals in igneous rock (Pettijohn, 1957), are much less stable and less common in sediments. In humid climates, feldspars are relatively easily decomposed to form products including clay minerals, silica, and oxides of aluminum.
