It involves the melting in the raw material employing oxyhydrogen flame as well as the crystallisation of the melted droplets to sort a cylinder. Graded 9 around the Mohs-hardness scale (graded one-10), the ensuing sapphire crystals are almost scratch-proof and really challenging, making sure an unhindered vision continually. Photo: HICONSUMPTION https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/