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Eolian action does not produce quartz particles between 20 and 50 microns in mass, either by abrasion of larger grains or by spalling of chips in that size range. Aqueous spalling is insignificant compared to disintegration of phyllite or similar material and of coarser crystalline rocks. Glacial action is particularly important.
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Ph. H. Kuenen (1969) studied this question.
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