It will involve the melting in the Uncooked compound employing oxyhydrogen flame plus the crystallisation from the melted droplets to sort a cylinder. Graded 9 over the Mohs-hardness scale (graded one-10), the resulting sapphire crystals are nearly scratch-evidence and really tricky, making sure an unhindered vision all of the time. https://www.watchesworld.com/top-10-dive-watches/