Round, white, pellets that can be used for a variety of uses; fertilizer and explosives come to mind. When mixed with zinc dust and water, ammonium nitrate produces water vapor that resembles a smoke screen. Add it to water and it creates a cooling, endothermic effect. Toss it on your grass and the nitrogen will make it very green; add it to your vegetable garden and you will get beautiful dark green leaves but no fruit. Learned that one the hard way.
LL Demos & Lab: Instant Cold Pack, Smokescreen on Demand
Click Here to Download the Ammonium Nitrate MSDS