It will involve the melting with the raw substance working with oxyhydrogen flame and the crystallisation of your melted droplets to kind a cylinder. Graded 9 over the Mohs-hardness scale (graded 1-10), the ensuing sapphire crystals are pretty much scratch-proof and very difficult, ensuring an unhindered eyesight constantly. Functional cookies https://www.watchesworld.com/top-10-dive-watches/