It consists of the melting on the raw substance employing oxyhydrogen flame plus the crystallisation on the melted droplets to sort a cylinder. Graded 9 on the Mohs-hardness scale (graded one-10), the ensuing sapphire crystals are pretty much scratch-evidence and very hard, making certain an unhindered vision at all times. https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/