Currently stones that look similar to dimonds (including synthetic) are widely used. They are called "imitation" and not a fake. The following stones are commonly used to imitate diamonds: 1. Natural stones , such as zircon, white sapphire, topaz, rock crystal; 2. Artificial stones , such as moissanite, titanite, stabilized zircon, lithium niobate, and others. Gemologists verify the luminescence of diamonds under UV light with a wavelength of 365 nm, rarely with a wavelength of 294nm. If the stone is illuminated with visible light, i. e. it luminesces, the color and light intensity is assessed by eye. The nature of luminescence in a diamond is a variety of optically active centers, mainly impurities at the atomic level. The most common center consisting of three nitrogen atoms and one vacancy, gives a blue luminescence, which is most common in diamonds. But it is considered that the color and intensity of the glow could be anything, and in rare cases it is phosphorescence, i. e. the stone glows in the dark even after the UV lamp turned off. The method of express diagnosis of diamonds is based on this phenomenon, especially if therere many diamonds in the product. The product is looked at under a UV lamp, the phianites are all inert while the diamonds light under the ultraviolet in different colors and with different intensity. However, this method is not 100 % relliable as for example, zircon can luminesce in UV rays as well. Diamonds have individual glow in the ultraviolet which is different for each stone. But imitations always light in the same way.
