If you have nothing but sand around you, you can still use it for hunting or to defend yourself: heated to a sufficient degree, sand becomes vitrified. In essence, it melts, and anything hot can become an exotic weapon if used properly
In ancient times, and particularly in coastal cities that often had to resist under siege the harassment of all sorts of invaders, sand was indeed used as a survival weapon. Sidon and Tyre in Lebanon are prime examples of this: the Assyrians and Babylonians often attacked these towns. The Sidonians and Tyreans used to toss by different means melted or very hot sand over the invaders over the top of their fortifications.
