It requires the melting with the raw material utilizing oxyhydrogen flame along with the crystallisation with the melted droplets to sort a cylinder. Graded nine around the Mohs-hardness scale (graded 1-10), the ensuing sapphire crystals are virtually scratch-evidence and really tough, making sure an unhindered eyesight all the time. The https://www.watchesworld.com/top-10-dive-watches/