It consists of the melting in the Uncooked substance using oxyhydrogen flame and also the crystallisation with the melted droplets to type a cylinder. Graded nine about the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are almost scratch-evidence and very really hard, ensuring an unhindered eyesight at all times. https://www.watchesworld.com/top-10-dive-watches/