380 nm to 750 nm), and extraordinarily scratch-resistant. The key benefits of sapphire windows are: Very wide optical transmission band from UV to near infrared (0.15–5.5 µm) Significantly stronger than other optical materials or standard glass windows Highly resistant to scratching and abrasion (9 on the Mohs scale of mineral hardness scale, the 3rd hardest natural substance next to moissanite and diamonds) Extremely high melting temperature (2030 °C) Some sapphire-glass windows are made from pure sapphire boules that have been grown in a specific crystal orientation, typically along the optical axis, the c axis, for minimum birefringence for the application. The boules are sliced up into the desired window thickness and finally polished to the desired surface finish. Sapphire optical windows can be polished to a wide range of surface finishes due to its crystal structure and its hardness. The surface finishes of optical windows are normally called out by the scratch-dig specifications in accordance with the globally adopted MIL-O-13830 specification. The sapphire windows are used in both high-pressure and vacuum chambers for spectroscopy, crystals in various watches, and windows in grocery-store barcode scanners, since the material's exceptional hardness and toughness makes it very resistant to scratching. In 2014 Apple consumed "one-fourth of the world’s supply of sapphire to cover the iPhone’s camera lens and fingerprint reader". Several attempts have been made to make sapphire screens for smartphones viable. Apple contracted GT Advanced Technologies, Inc. to manufacture sapphire screens for iPhones, but the venture failed resulting in the bankruptcy of GTAT. The Kyocera Brigadier was the first production smartphone to feature a sapphire screen. It is used for end windows on some high-powered laser tubes, as its wide-band transparency and thermal conductivity allow it to handle very high power densities in the infrared and UV spectrum without degrading due to heating. Along with zirconia and aluminum oxynitride, synthetic sapphire is used for shatter-resistant windows in armored vehicles and various military body armor suits, in association with composites. One type of xenon arc lamp originally called the "Cermax" and now known generically as the "ceramic-body xenon lamp" uses sapphire crystal output windows. This product tolerates higher thermal loads and thus higher output powers when compared with conventional Xe lamps with pure silica window. As substrate for semiconducting circuits Thin sapphire wafers were the first successful use of an insulating substrate upon which to deposit silicon to make the integrated circuits known