It consists of the melting on the raw substance working with oxyhydrogen flame and also the crystallisation of the melted droplets to sort a cylinder. Graded 9 on the Mohs-hardness scale (graded 1-ten), the ensuing sapphire crystals are practically scratch-proof and very really hard, making certain an unhindered eyesight constantly. https://www.watchesworld.com/top-10-dive-watches/