It consists of the melting in the raw material using oxyhydrogen flame as well as the crystallisation of the melted droplets to sort a cylinder. Graded nine to the Mohs-hardness scale (graded one-10), the resulting sapphire crystals are just about scratch-evidence and really challenging, making sure an unhindered eyesight always. https://www.watchesworld.com/top-10-dive-watches/