It includes the melting of the raw material employing oxyhydrogen flame along with the crystallisation with the melted droplets to variety a cylinder. Graded 9 to the Mohs-hardness scale (graded one-ten), the resulting sapphire crystals are just about scratch-proof and very tricky, ensuring an unhindered vision all of the time. https://www.watchesworld.com/top-10-dive-watches/