It involves the melting with the Uncooked compound utilizing oxyhydrogen flame as well as the crystallisation with the melted droplets to form a cylinder. Graded nine around the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are nearly scratch-evidence and very difficult, making certain an unhindered eyesight all the time. https://www.watchesworld.com/top-10-dive-watches/