It entails the melting with the Uncooked compound making use of oxyhydrogen flame plus the crystallisation with the melted droplets to kind a cylinder. Graded 9 about the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are practically scratch-evidence and very challenging, making sure an unhindered eyesight at all times. https://www.watchesworld.com/top-10-dive-watches/