Those are minerals, they are used to assign what the type of levels that will appear in each stratum of a dormant gate, (except boss ones, they cannot be altered.) Note that it is determined by the overall amount of minerals that each person in the community deposits, not just you. So it can be a bit stressful at times trying to get a gate to be a specific type. For further information, see one of the missions. I believe the name of this mission is: "Minerals Rock!"