John Brown Droste, George Willard White, Albert E. Vatter; Electron micrography of till matrix [Ohio]. Journal of Sedimentary Research ; 28 (3): 345–350. doi: https://doi.org/10.1306/74D707F9-2B21-11D7-8648000102C1865D
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Wisconsin tills from northeastern Ohio were studied under the electron microscope as fragments from less than 1 to several microns and on surfaces as large as 1/4 inch, using carbon replica techniques. Subhedral "grains" are composed of illite and chlorite; anhedral "grains" are kaolinite. Kaolinite is absent from "late" Cary (just pre-Defiance) till. Nonclay minerals, quartz, feldspar, and calcite, are either absent or exceedingly rare in less than 2 micron sizes, but increase in amount in larger sizes and are common in larger than 4 micron grain sizes. The platy clay minerals are oriented more or less parallel to the horizontal plane of the till in place.