It will involve the melting in the Uncooked compound employing oxyhydrogen flame plus the crystallisation in the melted droplets to form a cylinder. Graded 9 on the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are practically scratch-proof and very hard, making certain an unhindered vision all of the time. https://www.watchesworld.com/top-10-dive-watches/