It consists of the melting from the raw compound utilizing oxyhydrogen flame and also the crystallisation in the melted droplets to variety a cylinder. Graded nine over the Mohs-hardness scale (graded one-10), the resulting sapphire crystals are virtually scratch-proof and very hard, making sure an unhindered eyesight at all times. https://www.watchesworld.com/top-10-dive-watches/