It requires the melting with the Uncooked compound applying oxyhydrogen flame plus the crystallisation in the melted droplets to variety a cylinder. Graded nine around the Mohs-hardness scale (graded one-ten), the ensuing sapphire crystals are practically scratch-evidence and really difficult, ensuring an unhindered eyesight constantly. Later illustrations are available inside https://www.watchesworld.com/top-10-dive-watches/