It includes the melting in the Uncooked compound utilizing oxyhydrogen flame and also the crystallisation from the melted droplets to kind a cylinder. Graded nine within the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are just about scratch-evidence and very tough, making sure an unhindered eyesight at all times. https://www.watchesworld.com/top-10-dive-watches/