It entails the melting with the Uncooked substance using oxyhydrogen flame plus the crystallisation with the melted droplets to kind a cylinder. Graded 9 on the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are pretty much scratch-proof and very tricky, making sure an unhindered vision all the time. In https://www.watchesworld.com/top-10-dive-watches/