It requires the melting of your Uncooked substance making use of oxyhydrogen flame along with the crystallisation of the melted droplets to form a cylinder. Graded 9 to the Mohs-hardness scale (graded 1-ten), the resulting sapphire crystals are pretty much scratch-evidence and very hard, making certain an unhindered eyesight constantly. https://www.watchesworld.com/top-10-dive-watches/