It consists of the melting of the raw substance applying oxyhydrogen flame as well as crystallisation on the melted droplets to kind a cylinder. Graded 9 within the Mohs-hardness scale (graded one-10), the ensuing sapphire crystals are nearly scratch-evidence and very difficult, making certain an unhindered vision all the time. https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/