Low zircon’s crystal structure has been altered by thousands of years of irradiation from its own trace elements. It’s typically dark green. High zircon’s gemological properties are higher, so type can be determined with standard gemological testing. Most zircon used in jewelry is high zircon.
Make sure your invoice specifies that the spinel you are buying is natural. If you have any doubt, a report from the NQTC lab will confirm whether a spinel is natural.
The definition of padparadscha has always been debated. NQTC has studied the history of the term and its modern use and indicates on a Colored Stone Identification & Origin Report when a sapphire, in our opinion, meets the criteria to be described as padparadscha.
There is no official standard for Imperial topaz. Some dealers use the term for colors that are orange to pink to red to purple; others reserve the term for certain saturated shades. It’s the color, not the term “Imperial,” that gives topaz its value.
Although cobalt blue spinels do owe their vivid color to traces of cobalt, it’s the color that makes them valuable, not the presence of that coloring agent. If your spinel has a rich saturated blue color, it is rare and valuable whether or not it contains traces of cobalt.
Sapphires treated by lattice diffusion generally cost less than sapphires that have been treated by heat without the addition of color-causing chemicals or sapphires that have not been treated.
Heating is an accepted treatment for sapphire. But for fine-quality sapphire, confirmation from an independent laboratory like NQTC that there is no evidence of heat adds to a sapphire’s rarity and value.
Jadeite is available in a wide range of colors. In rare cases some could be considered pink; however, this material is referred to in the trade as lavender. Rare examples of Guatemalan jadeite in a blue color do exist. Terms like pink jade, Mexican jade, Alaska jade, Transvaal jade or Japanese jade generally refer to other minerals, which may be green or other colors.