It involves the melting of your raw compound using oxyhydrogen flame and the crystallisation of your melted droplets to sort a cylinder. Graded nine to the Mohs-hardness scale (graded 1-ten), the resulting sapphire crystals are almost scratch-proof and really really hard, making sure an unhindered vision constantly. Picture: HICONSUMPTION It https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/