It involves the melting with the Uncooked substance using oxyhydrogen flame as well as crystallisation in the melted droplets to type a cylinder. Graded nine within the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are almost scratch-proof and really challenging, making sure an unhindered vision continually. Useful cookies Practical https://www.watchesworld.com/top-10-dive-watches/