It requires the melting in the raw compound working with oxyhydrogen flame along with the crystallisation of the melted droplets to form a cylinder. Graded nine within the Mohs-hardness scale (graded 1-ten), the resulting sapphire crystals are nearly scratch-evidence and really challenging, ensuring an unhindered vision all of the time. https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/