It entails the melting of the raw compound employing oxyhydrogen flame and the crystallisation with the melted droplets to kind a cylinder. Graded 9 about the Mohs-hardness scale (graded one-10), the ensuing sapphire crystals are almost scratch-proof and really tricky, making certain an unhindered vision all of the time. Notably https://www.watchesworld.com/top-10-dive-watches/