Ultrasonic power is very effective in the mechanical analysis of fine-grained sedimentary rocks, such as clays, shales, and siltstones. An ultrasonic instrument which generates power from the tip of a cone-shaped mechanical transformer is much more effective than "tank-type" instruments. The ultrasonic method is very rapid and satisfactory for most fine-grained sedimentary rocks; however hard black shales are very refractory and require considerable time for complete disaggregation. Material coarser than clay-size is very satisfactorily disaggregated for size analysis; due to the micalike structure of some of the clay minerals, considerable alteration of grains probably occurs within the clay-size range, but this has no effect on size analysis for total sand, silt, and clay.

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