It entails the melting of your raw substance using oxyhydrogen flame plus the crystallisation of the melted droplets to sort a cylinder. Graded 9 around the Mohs-hardness scale (graded one-10), the resulting sapphire crystals are practically scratch-evidence and really difficult, making sure an unhindered eyesight constantly. Practical cookies Purposeful cookies https://www.watchesworld.com/top-10-dive-watches/