Corundum is a class of minerals, best known for the gem varieties such as ruby and sapphire, which are essentially the same mineral albeit of different colors. Corundum is a hard and highly stable mineral. It is the hardest mineral after diamond, making it the world's second hardest mineral for all practical purpose. Chemically Corundum is nothing but aluminum oxide and it can be easily synthesized industrially. Synthetic corundum can be manufactured by adding small quantities of color producing elements to the solution of Corundum, which is then left to solidify in a predetermined shape. The process of synthetic production of Corundum is known as Verneuil Process. Corundum minerals are available in different colors. The most common varieties of Corundum are Emery (Black), Padparadschah (Pink and orange variety of Sapphire), Ruby (Pink or red), Green Sapphire, Blue Sapprihe, Star Ruby, and Star Sapphire among some others.