It consists of the melting with the Uncooked compound working with oxyhydrogen flame and the crystallisation with the melted droplets to kind a cylinder. Graded 9 within the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are almost scratch-evidence and very hard, making certain an unhindered vision at all times. https://www.watchesworld.com/top-10-dive-watches/