According to the patent background:
“Corundum is a crystalline form of aluminum oxide and is found in various different colors, all of which are generally commonly referred to as sapphire except for red corundum which is commonly known as ruby and pinkish-orange corundum which is known as padparadscha. Transparent forms of corundum are considered precious stones or gems. Generally, corundum is extraordinarily hard with pure corundum defined to have 9.0 Mohs and, as such, is capable of scratching nearly all other minerals. For the present purposes, the terms “corundum” and “sapphire” may be used interchangeably to refer generally to the crystalline form of aluminum oxide.
As may be appreciated, due to certain characteristics of corundum, including its hardness and transparent characteristics, among others, it may be useful in a variety of different applications. However, the same characteristics that are beneficial for particular applications commonly increase both the cost and difficulty in processing and preparing the sapphire for those applications. As such, beyond costs associated with it being a precious stone, the costs of preparing the corundum for particular uses is often prohibitive. For example, the sapphire’s hardness makes cutting and polishing the material both difficult and time consuming when conventional processing techniques are implemented. Further, conventional processing tools such as cutters experience relatively rapid wear when used on corundum.”