It includes the melting with the Uncooked material utilizing oxyhydrogen flame and also the crystallisation in the melted droplets to form a cylinder. Graded 9 on the Mohs-hardness scale (graded one-ten), the resulting sapphire crystals are practically scratch-proof and very tough, making sure an unhindered vision always. Functional cookies Useful https://www.watchesworld.com/top-10-dive-watches/