It involves the melting on the raw substance applying oxyhydrogen flame plus the crystallisation on the melted droplets to kind a cylinder. Graded 9 over the Mohs-hardness scale (graded 1-ten), the resulting sapphire crystals are just about scratch-evidence and really challenging, making sure an unhindered eyesight all of the time. https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/