Chinese Turquoise is a soft, opaque gemstone. These gemstones sometimes have varying shades of colors ranging from blue-green, to yellow-green. They sometimes have a rock matrix and shades of Grey, black or brown veining to them. Much Chinese turquoise was used for carving and in other art and decorative ways. Turquoise jewelry, has always been popular in the Orient. In China, Turquoise dates to the thirteenth century A.D. Although mining did exist, most stone came from trade with the Persians, Turks, Tibetans, and the Mongols. Tibet had it's own source of turquoise usually a green cast, very hard stone with significant amount of spider webbing. The Tibetans highly revered the stone and was used in many areas as currency. Ancient doctors thought it to prevent injury through accident and would place perfect stones over the eyes to prevent blindness. They also ground it into a salve or powder to cure stomach disorders, internal bleeding, ailments of the hip and bites and stings. Turquoise is believed to protect the wearer from danger. In various countries, it is believed to fade when illness or danger is near. Another belief is that a fading stone indicates a lover's faithlessness or a friend's disaffection.