It involves the melting on the Uncooked material applying oxyhydrogen flame as well as the crystallisation of the melted droplets to sort a cylinder. Graded 9 about the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are nearly scratch-evidence and very tough, ensuring an unhindered vision continually. Useful cookies Functional https://www.watchesworld.com/top-10-dive-watches/