It entails the melting from the raw material using oxyhydrogen flame along with the crystallisation from the melted droplets to kind a cylinder. Graded nine about the Mohs-hardness scale (graded 1-ten), the resulting sapphire crystals are virtually scratch-proof and very difficult, making sure an unhindered eyesight all of the time. https://www.watchesworld.com/top-10-dive-watches/