It consists of the melting of the raw compound working with oxyhydrogen flame and also the crystallisation on the melted droplets to form a cylinder. Graded 9 about the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are almost scratch-evidence and really tricky, guaranteeing an unhindered vision always. four. Thickness https://www.watchesworld.com/the-most-coveted-watches-in-the-uk/