It includes the melting of the raw material working with oxyhydrogen flame plus the crystallisation with the melted droplets to variety a cylinder. Graded nine about the Mohs-hardness scale (graded 1-ten), the resulting sapphire crystals are pretty much scratch-evidence and very challenging, ensuring an unhindered eyesight all of the time. https://www.watchesworld.com/top-10-dive-watches/