It involves the melting of the Uncooked material applying oxyhydrogen flame along with the crystallisation from the melted droplets to kind a cylinder. Graded nine around the Mohs-hardness scale (graded 1-ten), the resulting sapphire crystals are pretty much scratch-proof and very challenging, making sure an unhindered vision all the time. https://www.watchesworld.com/top-10-dive-watches/