Editing Simpson Desert (section)

===Sediment===
The sand is predominately made up of [[quartz]] grains, which are [[Roundness (geology)|rounded and subangular]]. They range in size from 0.05 to 1.2&nbsp;mm with 0.5&nbsp;mm being the typical size for the crests and 0.3&nbsp;mm being the average size on the dune flanks. The active crests have sand sediment, but on the interdunes, the sediment is not as well sorted.<ref name=Twidale/> The sediment varies in colour from pink to brick red, but by the rivers and playas, the sediment colour is light grey. The progression of the colour from grey to red is due to the release of [[iron oxide]] from the sediment when weathered.<ref name=Twidale/>