It entails the melting with the Uncooked compound working with oxyhydrogen flame and the crystallisation with the melted droplets to form a cylinder. Graded 9 to the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are pretty much scratch-evidence and very difficult, guaranteeing an unhindered vision all of the time. https://www.watchesworld.com/top-10-dive-watches/