The September birthstone and 5th anniversary stone, sapphire is a natural blue variety of corundum. Sapphires can be found in a wide range of hues, including light blue, medium blue, deep blue, and deep purple.
Sapphire is one of the toughest gemstones, second only to diamond in hardness. It is used in a variety of industrial applications, including supermarket scanners and shatter-resistant windows in various military body armor suits.
Synthetic sapphire is also used in high-powered lasers. It can be tuned to different wavelengths of red and near-infrared radiation, and it is easily mode-locked. This makes it an excellent choice for end windows on laser tubes, as well as a substrate upon which to deposit silicon for integrated circuits known as “SOS” (silicon on insulator).
Some jewelers heat and then rapidly quench the surface of a ruby or sapphire, creating spider-web-like fissures that can be very difficult to remove. This practice is reflexive for many jewelers, but it can cause serious damage.
A good way to get a decent polish on a sapphire without spending much money is to use an old CD, some PVC adhesive, and a bit of diamond powder. A BATT or ceramic lap will work too, but they are more expensive and harder to get flat. Corian is another cheap option that works surprisingly well.