This Oxide found in nature as a mineral Corundum, which only exceeds in hardness by Diamonds and a few other synthetic substance, giving it EXCELLENT ABRASIVE qualities. For over 27 years, this Oxide has been used by the Dental Profession for polishing surgical implants, preparation of crowns and fillings and as an abrasive used directly against the tooth surface to clean off decay. These processes have been done world wide with no health problems associated with Oxide Crystals.