The cat's eye, or the cat's eye quartz, is, as the name suggests, a variation of the quartz. The mineral has a special appearance that is interesting and attractive for jewellery production. If the cat's eye is in its purest form, then it is almost colorless, however, it occurs much more frequently in the colors yellow and green. These colours are created in the popular mineral by the presence of foreign substances. Pseudomorphosis is also responsible for the characteristic yellow colouring. However, cat's eyes are not only popular because of their natural appearance as gemstones, they also get their typical look from their cut. This is usually done with cat eyes in the cabochon form, which means a round, oval shape of the gemstones. This is the only way that the cat's eye can develop its characteristics, because it is only through this cut that the chatoyance effect occurs, which gives the cat's eye its name. This effect is called the shimmer of the gemstone, which resembles the eye of the animal.