It consists of the melting on the raw material employing oxyhydrogen flame and also the crystallisation in the melted droplets to form a cylinder. Graded 9 on the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are nearly scratch-proof and really really hard, guaranteeing an unhindered vision all the time. https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/