It will involve the melting of your raw material working with oxyhydrogen flame as well as crystallisation on the melted droplets to form a cylinder. Graded 9 over the Mohs-hardness scale (graded one-10), the ensuing sapphire crystals are pretty much scratch-evidence and really tough, making sure an unhindered vision always. https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/