It will involve the melting in the raw material utilizing oxyhydrogen flame plus the crystallisation in the melted droplets to type a cylinder. Graded 9 around the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are pretty much scratch-proof and very difficult, making certain an unhindered eyesight all the time. https://www.watchesworld.com/top-10-dive-watches/