It involves the melting from the Uncooked compound applying oxyhydrogen flame plus the crystallisation with the melted droplets to type a cylinder. Graded nine about the Mohs-hardness scale (graded 1-ten), the resulting sapphire crystals are virtually scratch-proof and really tough, guaranteeing an unhindered vision all of the time. Useful cookies https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/