Turquoise is December's birthstone and recommended for a couple’s fifth wedding anniversary. With the gem in high demand and being much rarer than most people know, buyers must carefully assess a stone for quality. When shopping for Turquoise, review each stone’s signature color and the surrounding matrix. A buyer should also asses the stone's luster, a natural gemstone will have a much higher shine and glassy look. The higher the grade of Turquoise, the harder, and therefore greater shine the stone will have. Turquoise will vary in color from deep green to light blue while the surrounding hues may feature brown, white or black. Some gems may not feature varying colors within the stone. Keep in mind that the surrounding color does not cause the value of the gem to decrease. In fact, spiderweb Turquoise is some of the rarest and most valuable Turquoise there is. Therefore, individuals should decide whether they like more or less color variation in their turquoise jewelry.