It consists of the melting on the raw substance employing oxyhydrogen flame plus the crystallisation from the melted droplets to type a cylinder. Graded 9 within the Mohs-hardness scale (graded one-10), the ensuing sapphire crystals are just about scratch-evidence and really challenging, making certain an unhindered eyesight at all times. https://www.watchesworld.com/top-10-dive-watches/