It will involve the melting of the Uncooked substance using oxyhydrogen flame as well as the crystallisation of the melted droplets to form a cylinder. Graded nine about the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are nearly scratch-evidence and very hard, ensuring an unhindered vision all the time. https://www.watchesworld.com/top-10-dive-watches/