It entails the melting from the Uncooked substance using oxyhydrogen flame plus the crystallisation from the melted droplets to variety a cylinder. Graded nine on the Mohs-hardness scale (graded 1-ten), the ensuing sapphire crystals are virtually scratch-evidence and very hard, ensuring an unhindered vision constantly. Useful cookies Useful cookies These https://www.watchesworld.com/top-10-dive-watches/