It involves the melting of your raw substance employing oxyhydrogen flame as well as crystallisation from the melted droplets to type a cylinder. Graded nine to the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are practically scratch-proof and very tricky, making certain an unhindered vision all of the time. https://www.watchesworld.com/top-10-dive-watches/