The Simpson Desert is a sandy desert. It's sedimentary sand grains are predominately made up of rounded quartz grains. Sturt's Stony Desert is an example of a gibber desert.
Yes, the desert is just one part of a large desert region covering much of the Australian continent. The Great Victoria and Tanami Deserts are two that are adjacent.
Not all deserts are sandy, though many are.
Sand is made primarily of silicon and oxygen.
If you look at the elemental composition of the Earth's crust, guess what the top two elements are? Did you...