Apple CEO Tim Cook described the company’s eagerly anticipated watch as ‘the most personal device we’ve ever created’. And it may be the California-based firm’s most durable too. A sapphire glass screen used in the device has remained scratch-free after being subjected to being rubbed with sandpaper, keyed and even hit with a hammer. Scroll down for video . A sapphire glass screen used in the device has remained unscratched after being subjected to being rubbed against a stone wall (pictured) and with sandpaper, keyed and even hit with a hammer . The test was carried out by Cardiff-based iPhone repairs specialist iPhoneFixed.co.uk, which used a sapphire screen from a 38mm Apple Watch for its experiment. Two out of the three models of Apple Watches, which are available to pre-order from today, have sapphire glass screens. Two out of the three models of Apple Watches, which are available to pre-order from today, have sapphire glass screens. The only one that doesn't is the Sport model (pictured above) The glass is made from synthetic sapphire, which is created by applying heat and pressure to aluminium oxide powder, before being processed to remove impurities. Here, it withstands being scratched by sandpaper . Synthetic sapphire is a hard, transparent material made of crystallising aluminium oxide, produced at high temperatures and pressures. As the material is heated, it forms disks that can be sliced using diamond-coated saws. These round disks are ground into shape, and polished, to become glass. The resulting glass is thin, super-strong and scratch resistant. Apple already uses sapphire crystal in the Touch ID fingerprint scanner on the iPhone 5S and 6, as well as to protect the phones’ camera. The Apple Watch and Apple Watch Edition both have sapphire glass screens, while the Sport version has a strengthened Ion-X glass screen, which is thought to be more shatterproof. If the price of manufacturing the glass drops, it could potentially replace Gorilla Glass currently used in most high-end smartphones. The glass is made from synthetic sapphire, which is created by applying heat and pressure to aluminium oxide powder, before the crystals are processed to remove impurities. The tiny round disks created are ground into shape, and polished, to become glass. Sapphire glass is said to be twice as tough as normal glass and almost as hard as a diamond. The regular version, which costs from $549 (£479) and the Edition watch, from $12,000 (£8,000) both have sapphire glass screens, while the cheaper 'Sport' version, costing from $349 (£299) has a strengthened Ion-X glass screen, which iPhoneFixed describes as ‘more shatterproof and impact resistant than sapphire glass'. To test the durability of the screen, it was rubbed against a stone wall and then with a coin, before being ‘scratched’ by a key. The video capturing the attempts at destruction, shows no scratches were achieved to the screen. It also withstood being rubbed with abrasive sandpaper at some force and hit by a hammer – albeit not very hard. The video showing the attempts at destruction, shows no scratches were achieved to the screen, even when a power drill was switched on and dragged across it (pictured) But most impressive, was the screen’s ability to withstand an electric drill being dragged across its surface, without leaving a mark. The test led iPhoneFixed to claim: ‘sapphire glass is pretty strong and virtually impossible to scratch’. Rumours abounded that the iPhone 6 would get a sapphire screen, but it didn’t, possibly because the material is expensive to make when compared with standard of tough Gorilla Glass. The test led iPhoneFixed to claim: ‘sapphire glass is pretty strong and virtually impossible to scratch’. Apple has revealed it will only accept online orders for its much-anticipated watch which goes on sale on the 24th April. The firm will show off the watch to the public for the first time from tomorrow at its retail stores and several special popup stores around the world. From tomorrow morning, customers will be able to pre-order their watch online. 'Starting Friday, customers can try on Apple Watch, Apple Watch Sport or Apple Watch Edition to find the model with the size, finish and band to best fit their personal preference and style,' the firm explained. 'Everyone visiting an Apple Store will be able to view all three collections and get hands on with Apple Watch Demo to browse and edit different watch faces, and learn about Apple Watch's health and fitness features, Digital Touch, Siri and more.' Based on a survey in the United States on consumer interest in buying the Apple Watch, BMO Capital Markets has cut its estimate for sales to 39 million units though September 2016.
Two out of three versions of the Apple Watch have sapphire glass screens .
Test showed how durable the material made from synthetic crystals is .
Endured being sanded, keyed, rubbed, struck by a hammer and drilled .