It requires the melting of the raw material using oxyhydrogen flame as well as crystallisation with the melted droplets to form a cylinder. Graded nine to the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are pretty much scratch-evidence and really really hard, making sure an unhindered eyesight continually. Our https://www.watchesworld.com/top-10-dive-watches/