It consists of the melting from the Uncooked material applying oxyhydrogen flame and the crystallisation in the melted droplets to type a cylinder. Graded 9 within the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are just about scratch-proof and really tough, ensuring an unhindered vision all of the time. https://www.watchesworld.com/top-10-dive-watches/