It requires the melting on the Uncooked substance utilizing oxyhydrogen flame as well as the crystallisation of the melted droplets to type a cylinder. Graded 9 around the Mohs-hardness scale (graded one-10), the resulting sapphire crystals are nearly scratch-proof and really tricky, making sure an unhindered eyesight at all times. https://www.watchesworld.com/top-10-dive-watches/