It consists of the melting in the Uncooked material working with oxyhydrogen flame and the crystallisation from the melted droplets to variety a cylinder. Graded 9 to the Mohs-hardness scale (graded one-10), the resulting sapphire crystals are pretty much scratch-evidence and really challenging, ensuring an unhindered eyesight all the time. https://www.watchesworld.com/top-10-dive-watches/