It entails the melting of the Uncooked material employing oxyhydrogen flame and also the crystallisation from the melted droplets to form a cylinder. Graded nine over the Mohs-hardness scale (graded one-10), the ensuing sapphire crystals are pretty much scratch-proof and very hard, making sure an unhindered eyesight all the time. https://www.watchesworld.com/top-10-dive-watches/