It requires the melting with the raw material working with oxyhydrogen flame as well as the crystallisation on the melted droplets to variety a cylinder. Graded 9 about the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are pretty much scratch-proof and really tough, making certain an unhindered vision continually. https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/