Arid places typically have layered soil like this. The water never stays saturated on the top level. So in wild arid areas you will find these little rock clumps like decomposed granite, gypsum clumps, and even sandstone gravels. They are a cap for the soil below. And when the earth shifts below it they get broken up and make there way to the surface. I use decomposed granite for all my arid guys and its a great soil level system for growing succulenta. China should have it somewhere to buy.
