It requires the melting from the Uncooked substance employing oxyhydrogen flame and also the crystallisation of the melted droplets to type a cylinder. Graded nine on the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are nearly scratch-proof and very hard, guaranteeing an unhindered eyesight all of the time. Photograph: https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/