It involves the melting on the Uncooked substance using oxyhydrogen flame and also the crystallisation of the melted droplets to form a cylinder. Graded nine to the Mohs-hardness scale (graded 1-ten), the resulting sapphire crystals are nearly scratch-evidence and really tricky, making certain an unhindered vision all of the time. https://www.watchesworld.com/top-10-dive-watches/