It consists of the melting in the raw material making use of oxyhydrogen flame and also the crystallisation from the melted droplets to variety a cylinder. Graded 9 around the Mohs-hardness scale (graded 1-ten), the resulting sapphire crystals are pretty much scratch-proof and very hard, making certain an unhindered vision https://www.watchesworld.com/top-10-dive-watches/