Gemstone irradiation produce mixtures of blue and yellow-to-brown colors, so heating is required as an additional procedure to remove the yellowish color. In some cases, the new colors induced by artificial irradiation may fade rapidly when exposed to light or gentle heat, so some laboratories submit them to a "fade test" to determine color stability. Sometimes colorless or pink beryls become deep blue upon irradiation, which are called Maxixe-type beryl. However, the color easily fades when exposed to heat or light, so it has no practical jewelry application. Gemstone irradiation The gemstone irradiation is a process in which a gemstone is artificially
Diamond (gemstone) are often quoted per carat, rather than per stone. "Total carat weight" (t.c.w.) is a phrase used to describe the total mass of diamonds or other gemstone in a piece of jewelry, when more than one gemstone is used. Diamond solitaire earrings, for example, are usually quoted in t.c.w. when placed for sale, indicating the mass of the diamonds in both earrings and not each individual diamond. T.c.w. is also widely used for diamond necklaces, bracelets and other similar jewelry pieces. Clarity is a measure of internal defects of a diamond called "inclusions". Inclusions may be crystals of a foreign