It consists of the melting on the raw substance using oxyhydrogen flame as well as crystallisation on the melted droplets to variety a cylinder. Graded 9 within the Mohs-hardness scale (graded 1-10), the ensuing sapphire crystals are practically scratch-proof and really tricky, making certain an unhindered vision all the time. https://www.watchesworld.com/top-10-dive-watches/