Desert sand mostly originates from the weathering of rocks.

Rocks on Earth’s surface face constant changes. The sun heats them up during the day and cools them at night. This heating and cooling cause cracks. Wind and rain then break these rocks into smaller pieces. Over time, these pieces become sand grains. This process is called weathering. In deserts, where there is little rain and few plants, wind plays a big role in breaking down rocks and moving the sand around.