It consists of the melting with the raw material employing oxyhydrogen flame as well as the crystallisation of the melted droplets to form a cylinder. Graded nine on the Mohs-hardness scale (graded 1-10), the ensuing sapphire crystals are pretty much scratch-evidence and very hard, making certain an unhindered eyesight constantly. https://www.watchesworld.com/top-10-dive-watches/