Sand =! Industrial usable Sand. Not all kind of "Sand" is suited for the industry(today). Most desert/dune sand is to fine grained and has a smooth surface, so that it is unusable to create strong material. There are some projects/studies already that use "desert sand + X" to create "strong" material.
http://www.resourcepanel.org/reports/global-material-flows-a...
https://na.unep.net/geas/archive/pdfs/GEAS_Mar2014_Sand_Mini...