It involves the melting of the raw substance working with oxyhydrogen flame and also the crystallisation in the melted droplets to variety a cylinder. Graded 9 over the Mohs-hardness scale (graded one-ten), the resulting sapphire crystals are practically scratch-evidence and really hard, guaranteeing an unhindered eyesight always. The Superocean Heritage https://www.watchesworld.com/top-10-dive-watches/