Niter

Niter (alt. "nitre"), or in full Potassium Nitrate, sometimes called "saltpeter" (alt. "saltpetre"), is a rare mineral powder element found deep within the world. Despite its relative rarity, it is quite necessary for nuclear reactors of all kinds constantly.

Uses
When mixed with water to make Coolant, it has the properties of being able to cool down reactors by moving the heat to another location where it can either be utilized or dispersed. It can be mixed with water to create coolant for a reactor or it can be mixed on the spot by putting a niter block right next to a Small Nuclear Reactor so that it never runs out of coolant.

Niter is also used for explosives. It can be used to make Solid Rocket Fuel and Semtex.

Trivia

 * IRL, it is usually used to make fertilizer and gunpowder.
 * You can make gunpowder from niter in the mod too.
 * It can also be used as a reverse aphrodisiac in men, though this hasn't been confirmed by anyone.
 * Its name "saltpeter" roughly originates from old the term for "salt of the rock".
 * This is simply because it looks like salt and comes from rocks in caves.