It consists of the melting of your Uncooked compound using oxyhydrogen flame and also the crystallisation of your melted droplets to form a cylinder. Graded nine to the Mohs-hardness scale (graded one-10), the ensuing sapphire crystals are practically scratch-evidence and really challenging, making sure an unhindered vision at all times. https://www.watchesworld.com/top-10-dive-watches/