It will involve the melting in the raw substance employing oxyhydrogen flame as well as the crystallisation of the melted droplets to sort a cylinder. Graded 9 within the Mohs-hardness scale (graded one-10), the resulting sapphire crystals are pretty much scratch-proof and really difficult, making sure an unhindered eyesight all https://www.watchesworld.com/top-10-dive-watches/