It involves the melting with the raw compound applying oxyhydrogen flame as well as the crystallisation in the melted droplets to kind a cylinder. Graded nine around the Mohs-hardness scale (graded 1-ten), the ensuing sapphire crystals are almost scratch-proof and really really hard, guaranteeing an unhindered eyesight all the time. https://www.watchesworld.com/top-10-dive-watches/