It involves the melting of your raw compound utilizing oxyhydrogen flame and also the crystallisation with the melted droplets to form a cylinder. Graded nine to the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are practically scratch-evidence and very hard, making certain an unhindered eyesight all of the time. https://www.watchesworld.com/top-10-dive-watches/