It includes the melting of your raw material employing oxyhydrogen flame and also the crystallisation with the melted droplets to sort a cylinder. Graded nine about the Mohs-hardness scale (graded one-10), the resulting sapphire crystals are almost scratch-proof and really tough, making sure an unhindered eyesight all of the time. https://www.watchesworld.com/top-10-dive-watches/