It requires the melting of the Uncooked material making use of oxyhydrogen flame as well as the crystallisation of your melted droplets to form a cylinder. Graded nine around the Mohs-hardness scale (graded 1-ten), the resulting sapphire crystals are just about scratch-evidence and very hard, making sure an unhindered vision https://www.watchesworld.com/top-10-dive-watches/