Various reflecting surfaces were used: polished metallic rocks such as obsidian, pyrite, and iron; rock crystal; and an alloy of rose copper and tin, plus an alchemical brew consisting of white arsenic, red tartar, and nitre .
Maybe Boone noticed crystals of potassium nitrate there, because the deep, loose floor was soon being mined for niter to make gunpowder.
Nitre, or niter , is also used to manufacture gunpowder.
The fresh juice supplying 30 percent potassium and the mucilage a good amount of niter and sodium.
The German U-boats were shooting on the boats, so most of the niter they were trying to import to make nitroglycerin was at the bottom of the ocean.