It consists of the melting on the Uncooked material using oxyhydrogen flame as well as crystallisation on the melted droplets to form a cylinder. Graded 9 to the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are practically scratch-proof and very tough, guaranteeing an unhindered eyesight all of the time. https://www.watchesworld.com/top-10-dive-watches/