It consists of the melting with the Uncooked substance making use of oxyhydrogen flame plus the crystallisation of the melted droplets to type a cylinder. Graded nine around the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are virtually scratch-evidence and very difficult, ensuring an unhindered vision at all times. https://www.watchesworld.com/top-10-dive-watches/