It consists of the melting in the raw compound utilizing oxyhydrogen flame and the crystallisation of the melted droplets to kind a cylinder. Graded 9 around the Mohs-hardness scale (graded one-10), the resulting sapphire crystals are pretty much scratch-proof and really tough, making sure an unhindered vision at all times. https://www.watchesworld.com/top-10-dive-watches/