Cat essence, also known as opal, is mainly composed of oxygen, lead and beryllium. Yellow-green, fragile, glassy. This is a kind of gem. When used as an ornament, it is often ground into a ball, which looks like a cat's eye, commonly known as opal.

Cat's eye is the scientific name of cat essence, that is, cat's eye, opal and cat essence. Opal, also known as oriental cat's eye, is a rare and precious variety in jewelry. Opal is named because it is as flexible and bright as a cat's eye and can change with the intensity of light. This optical effect is called cat's eye effect.