Why is quartz abundant in soils?

Answer 1

Quartz is abundant in soils for three reasons. First, it is an abundant mineral to begin with. Second, it is hard and tough; it doesn't break up and crumble into smaller and smaller pieces very easily. Third, it's more resistant to water and weathering than most other minerals you'll find at the surface of the Earth.

Consider granite. It contains quartz, feldspar, and mica. Water eventually degrades the feldspar and mica to clay minerals, but it leaves the quartz behind.