ABSTRACT

Literature on morphology of desert quartz grains is reviewed. Most works claim that desert sands are typically well-rounded and frosted by abrasion. By contrast, Simpson desert grains are subangular to angular, and no noticeable rounding is being accomplished in the present desert dune environment. This is probably because the Simpson desert consists of longitudinal dunes and the sand grains do not move back and forth as is the case with complex dunes. There is a small proportion of inherited rounded grains.

No abrasional surface features are being produced in the present environment. Silica is being precipitated as scabby, "turtle-skin" crusts on top of the grains, imparting a very characteristic greasy luster to the dune sands. The source of the silica is most likely solution of opal phytoliths, and reprecipitation of the silica as the containing water evaporates deeper within the dunes.