It consists of the melting on the raw compound working with oxyhydrogen flame along with the crystallisation from the melted droplets to type a cylinder. Graded nine within the Mohs-hardness scale (graded 1-10), the ensuing sapphire crystals are practically scratch-proof and really tricky, guaranteeing an unhindered vision all the time. https://www.watchesworld.com/top-10-dive-watches/