It involves the melting of the Uncooked compound making use of oxyhydrogen flame and the crystallisation of the melted droplets to variety a cylinder. Graded nine about the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are virtually scratch-proof and really difficult, making certain an unhindered vision all the time. https://www.watchesworld.com/top-10-dive-watches/