It will involve the melting of the raw compound using oxyhydrogen flame and the crystallisation in the melted droplets to kind a cylinder. Graded 9 over the Mohs-hardness scale (graded one-10), the resulting sapphire crystals are almost scratch-proof and really really hard, guaranteeing an unhindered vision at all times. Readily https://www.watchesworld.com/top-10-dive-watches/