Ruby is a kind of corundum, or more precisely an aluminum oxide (Al2O3) minerals.
Although corundum is naturally colorless and transparent when mixed with chromium, a ruby red color appears. In the early 1900s the French scientist Verneuil invented his own methodology to produce ruby and the world's first artificial jewel stone was manufactured. In this methodology, aluminum oxide powder mixed with chromium is melted in a flame above 2000 degrees Celsius and then cooled down to be recrystallized. To this day, a large amount of ruby is still produced by the Verneuil process.
Since ruby is second only to diamond in hardness, it is often used for industrial applications. Orbray was the first to use it as a jewel bearing for watches. Ruby has excellent wear resistance, and it is widely used in luxury watches due to its beautiful appearance. In addition, it is used in measuring instruments, ruby scalpels, and as a light source for lasers.