How to distinguish a real yellow sapphire from a fake
A precious gem such as yellow sapphire has imitations and fakes. Glass (paste) is the most budgetary imitation. In such modern imitations like sital it turns out to achieve optical properties that are close to the characteristics of natural corundums. They can be distinguished by gas bubbles, sometimes large enough when viewed through a polariscope. The samples show a picture of anomalous anisotropy, beams, and stress zones. The refractive index of natural corundum will be quite high for glass and sital. In corundum the hardness is 9 on the Mohs scale, in glasses – 5-6. The most accurate imitation can be considered a synthetic analogue of yellow sapphire – man made yellow corundum. Its chemical composition, properties and appearance in faceted form are as close as possible to natural stone.
Currently, technology allows to obtain a wide range of shades corresponding to the natural color, depending on the addition and concentration of coloring impurities. Often, cubic zirconia is used as an imitation of yellow sapphire. Its high characteristics (dispersion, hardness, refractive index) provide a spectacular appearance of faceted stones. However, brightness of cubic zirconia even with the naked eye, allowing you to understand what kind of material is in front of you. Still, natural yellow sapphire has a more modest noble luster.
Also, natural golden corundum in some cases shows similarities with other stones. The most common comparison with fancy-colored diamonds. Citrine, gold imperial topaz, zircon, and occasionally chrysoberyl are also considered similar.