The blue cast is caused by very fine crystals of albite, the white sheen is caused by thick layers of albite. This color play is one way the gem can be found. Another of its varieties can show a cat’s eye effect. While most cat’s eye effects are caused by rutile inclusions within the gemstone, the cat’s eye effect in a moonstone is a matter of concentrating the internal reflection of the center of the cabochon gem. This concentrated reflection creates a bright center area down the center of the gem. The cat’s eye effect in a moonstone is much less defined than in other gems. The line is wider and looks more like a center glow than a hard line. There are two different effects that moonstone can display, the opalescence or the cat’s eye. In both cases the more transparent the gems, the more highly regarded. If the stone gets too cloudy or overall milky, the optical effects seem to get overshadowed. When looking for the cat’s eye effect, it all is a question of brightness and separating itself from the body color of the stone. The finest examples that show the color play or opalescence are the stones that have more blue and lavender flashes. Moonstones are mined in multiple locations, but the major producers are the United States, Sri Lanka (Ceylon), Austria, Norway, and Poland. The most known color of moonstone is the milky white body color. That is how it forms in nature in a pure form. However, if other elements enter the crystal as it is forming it can start to impact the body color. The colors may be beige, brown, greenish, or yellowish.