It involves the melting on the raw material applying oxyhydrogen flame and the crystallisation in the melted droplets to type a cylinder. Graded 9 over the Mohs-hardness scale (graded one-ten), the resulting sapphire crystals are nearly scratch-evidence and really difficult, ensuring an unhindered eyesight all the time. The Superocean Heritage https://www.watchesworld.com/top-10-dive-watches/