It involves the melting from the raw compound making use of oxyhydrogen flame plus the crystallisation from the melted droplets to form a cylinder. Graded nine within the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are practically scratch-evidence and really tough, making certain an unhindered eyesight at all times. https://www.watchesworld.com/top-10-dive-watches/