Katzenauge

Katzenauge is a German term that translates to "cat's eye" in English. It most commonly refers to a specific type of gemstone that exhibits a phenomenon known as chatoyancy. This optical effect causes a band of light to appear to move across the surface of the stone, resembling the slit pupil of a cat's eye.

The most well-known gemstone exhibiting chatoyancy is chrysoberyl, often referred to as cat's eye chrysoberyl. This stone is typically yellowish-green to brown in color. The chatoyant band is caused by the presence of parallel needle-like inclusions within the gemstone. When light hits these inclusions, it reflects in a single, concentrated band.

Other gemstones can also display chatoyancy and are sometimes referred to as cat's eye, though they are often qualified with the mineral name, such as tiger's eye (a quartz variety) or cat's eye tourmaline. The intensity and sharpness of the cat's eye effect depend on the quality and orientation of the inclusions. A well-formed cat's eye gemstone will have a sharp, distinct band that runs across the widest part of the cabochon-cut stone.

In addition to its use in jewelry, the cat's eye effect is considered a desirable characteristic that can increase a gemstone's value. The term "Katzenauge" is primarily used in German-speaking regions when discussing these chatoyant gemstones.