A Tretise on Rocks, Rock-Weathering and Soils (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1906 Excerpt: ...lineal inch, and which represents the impalpable mud remaining in suspension while the 6.5% of fine sand sank quickly to the bottom of the beaker in which the washing was made. The residual sand yielded then: The coarser of these particles, like the gravel and coarse sand, are of a compound nature, aggregates of quartz and feldspar, with small amounts of mica and other minerals. In the finer material, on the other hand, each particle represents but a single mineral, the process of disaggregation having quite freed it from its associates, excepting of course, the microscopic inclusions which could be liberated only by a complete disintegration of the host itself. These particles, as seen under the microscope, are all sharply angular, and in many cases surprisingly fresh, though the analyses had suggested only a slight change in chemical composition. The mica shows the greatest amount of alteration, the change consisting mainly in an oxidation of its ferruginous constituent, whereby the folia becomes stained and reduced to yellowish brown shreds. The feldspars are, in some cases, opaque through kaolinization, but in others are still fresh and unchanged even in the smallest particles. The finest silt, when treated with a diluted acid to remove the iron stains, shows the remaining granules of quartz, feldspar, and epidote beautifully fresh, and with sharp, angular borders, the mica being, however, almost completely decolorized. An analysis of the silt, which was found to constitute 4.25% of the entire mass of disintegrated material, as noted above, is given below, and also a partial separation and analysis of the 39.7% soluble, and 60.3% insoluble portions.1 From these analyses it would appear that of the 17 grammes of silt, representing 4% of the total disinte...