It includes the melting of the Uncooked compound employing oxyhydrogen flame plus the crystallisation of the melted droplets to form a cylinder. Graded nine over the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are pretty much scratch-evidence and very hard, making certain an unhindered vision all the time. Returns https://www.watchesworld.com/top-10-dive-watches/