It entails the melting from the Uncooked compound employing oxyhydrogen flame and the crystallisation in the melted droplets to type a cylinder. Graded nine within the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are pretty much scratch-proof and very difficult, making certain an unhindered vision all of the time. https://www.watchesworld.com/top-10-dive-watches/