It requires the melting in the raw substance working with oxyhydrogen flame as well as crystallisation with the melted droplets to form a cylinder. Graded nine to the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are practically scratch-proof and really difficult, ensuring an unhindered vision all of the time. https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/