The term "ore" is used in connection with a rock or mineral mass when it contains enough of an element or compound to make it economically feasible to mine. 15 specimens of the more important ores are included. Grades 6-12. Ages 11-18. The term "ore" is used in connection with a rock or mineral mass when it contains enough of an element or compound to make it economically feasible to mine. 15 specimens of the more important ores are included. Grades 6-12. Ages 11-18.