It requires the melting of the raw compound using oxyhydrogen flame as well as the crystallisation of the melted droplets to form a cylinder. Graded nine to the Mohs-hardness scale (graded 1-10), the resulting sapphire crystals are just about scratch-proof and very tricky, making certain an unhindered eyesight constantly. The https://www.watchesworld.com/top-10-dive-watches/