For many, a gem’s desirability is largely dependant on it’s banding (the thinner and clearer this effect, the rarer and more sought-after the gem). You May Also Like 25.97-carat emerald found by Toronto miner Chatoyancy (Cat’s eye)Ĭhatoyancy is the appearance of a luminous band, generally white, which slides on the surface of a cabochon under a light and creates an effect reminiscent of the slit of a cat’s eye. Though it is iridescence, many in the pearl business more often than not call the effect ‘the Orient.’ Iris quartz is one of the few gemstones in which the iridescence is entirely caused by fissures inside. Nacre and pearl are each composed of layers upon layers of conchiolin and aragonite. For example, in Labradorite, the labradorescence is caused by the overlapping thin layers of calcium and sodium, while fire agate contains thin layers of iron oxide inside a quartz. More often than not, the iridescence, adularescence, and/or labradorescence observed in a gemstone is caused by the reflection and interference of light on layers inside the stone. Simply put, because Labradorite and moonstone are from the same family (called feldspar), the gemmology community decided to name the optical effect differently for the two gems. Like iridescence and adularescence, labradorescence (observed in Labradorite) is also the reflection and interference of light inside a gemstone. The light is diffused inside and creates the blue sheen. Like iridescence, this blue can be seen moving, depending on the incident light change. Popular examples of iridescence in gemstones include rainbow garnet (mostly from Japan), fire agate, pearl, nacre, iris agate, and rainbow obsidian.Īdularescence, seen in moonstone, is blue or white reflection observed inside a gemstone. Some industry professionals consider it the same iridescence you can also observe in a fissure or a broken stone, while others do not consider this an optical phenomenon. The colourful sheen can also be seen shifting, depending on the incident light change and how a gemstone is moved. Iridescence, for instance, is a lot like adularescence however, while the latter primarily offers a blue lustre, iridescence can show all colours of the rainbow in the reflection observed inside a gemstone. In gemmology, iridescence, adularescence, and labradorescence are often grouped together, but each offers its own unique beauty. Iridescence, adularescence, and labradorescence sapphire, ruby, beryl, etc.) can have the optical phenomenon. spinel, garnet, diamond, etc.) are not able to have any pleochroism only the anisotropic gemstones ( e.g. The aforementioned is the result of the light’s polarization in two vibrant perpendicular rays. Pleochroism is mainly attributed to the differential selective absorption of wave lengths.
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