Turquoise is an opaque blue to green colored gemstone. One of the oldest used gemstones, Turquoise has been used in Ancient Egyptian, Aztec, and Persian Jewelry. The Persian scholar Al-Qazwini wrote: "The hand that wears a turquoise and seals with it will never see poverty." The colors found in turquoise occur due to copper and iron content. The more blue, the more copper it contains, and the more green, the more iron it has. The highest quality turquoise is considered to be a lightly colored sky blue with fine regular veins running through it. Turquoise is a December birthstone.