It entails the melting of the Uncooked compound using oxyhydrogen flame as well as the crystallisation from the melted droplets to sort a cylinder. Graded 9 about the Mohs-hardness scale (graded 1-10), the ensuing sapphire crystals are virtually scratch-evidence and very hard, ensuring an unhindered eyesight all of the time. https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/