What is the Definition of Emery?

Emery is a dense, non-porous fine-grained aggregate produced from naturally occurring Emery ore that is rich in aluminum oxide. Mineralogically, Emery is an intimate mix of corundum, a natural form of aluminum oxide, and magnetite. It is this percentage of aluminum oxide in Emery which makes Emerundum so extremely hard, tough, and fracture resistant. Emerundum is crushed only from specially selected abrasive Emery ore that contains not less than 58% aluminum oxide.