It consists of the melting on the Uncooked material employing oxyhydrogen flame and also the crystallisation of the melted droplets to type a cylinder. Graded nine over the Mohs-hardness scale (graded 1-ten), the ensuing sapphire crystals are pretty much scratch-proof and very tough, guaranteeing an unhindered eyesight all the time. https://www.watchesworld.com/top-10-dive-watches/