It entails the melting in the raw compound using oxyhydrogen flame along with the crystallisation from the melted droplets to sort a cylinder. Graded nine over the Mohs-hardness scale (graded 1-ten), the ensuing sapphire crystals are pretty much scratch-evidence and really tricky, making sure an unhindered vision all the time. https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/