This type of cut results in smooth, polished convex surface that are egg or oval shaped. As opposed to the facet cuts previously mentioned, the cabochon cut is usually used in gemstones that are less transparent (opaque) or have many impurities in them. Such gemstones usually employ cabochon cut to accentuate their colors, such as jades, rubies and sapphires. Gemstones with optical phenomena such as asterisms, chatoyancy (cat-eye) and color change are usually cut in the style of Cabochon to accentuate their phenomena, such as cat's eye chrysoberyls, asteriated rubies and blue sapphires, opals and nephrites.