What is the primary cause of frosting present in the surface of quartz sand grains in the desert?

The primary cause of frosting on the surface of quartz sand grains in the desert is the process of wind abrasion. As wind-blown sand particles collide with quartz grains, they chip away tiny fragments from the surface, creating a textured, frosted appearance. This weathering process is enhanced by the arid conditions, which limit moisture and vegetation, allowing for more intense and continuous abrasion. Over time, this results in the characteristic frosted look of desert sand grains.