It will involve the melting in the raw material working with oxyhydrogen flame along with the crystallisation on the melted droplets to form a cylinder. Graded 9 on the Mohs-hardness scale (graded 1-10), the ensuing sapphire crystals are just about scratch-evidence and really tough, making sure an unhindered eyesight all https://www.watchesworld.com/top-10-dive-watches/