It will involve the melting of the raw substance working with oxyhydrogen flame and also the crystallisation on the melted droplets to type a cylinder. Graded 9 on the Mohs-hardness scale (graded 1-ten), the resulting sapphire crystals are nearly scratch-evidence and really challenging, guaranteeing an unhindered eyesight all the time. https://www.watchesworld.com/top-10-dive-watches/