[(NH4)2Cr2O7] Orange granular
Ammonium Dichromate is an oxidizer used in Skylighter's Volcano Science Project. Sometimes used as a burn rate catalyst in propellant formulas (such as those based on ammonium nitrate). Also used to suppress the reaction of magnesium in ammonium perchlorate compositions.
Here's a full set of instructions on How to make a volcano with Ammonium Dichromate. This project is perfect for school demonstrations or kids science fairs.