It will involve the melting of the raw compound making use of oxyhydrogen flame along with the crystallisation with the melted droplets to form a cylinder. Graded 9 over the Mohs-hardness scale (graded one-ten), the resulting sapphire crystals are practically scratch-evidence and very difficult, making sure an unhindered vision continually. https://www.watchesworld.com/top-10-dive-watches/