The new "jade" is actually a form of light green serpentine, not jade. This tradename was given to the stone because it resembles jade in look and has comparable metaphysical characteristics. New "jade" and other serpentine minerals are recognized for their ease of cutting and polishing. The name "jade" was originally applied to any green stone but is now used primarily for emeralds and aquamarines. The difference between jade and nephrite is that jade is purer than nephrite. Therefore, jade is more valuable. Also, jade tends to be larger in size than nephrite. There are several varieties of jade. The most important variety for jewelry is the white jade, which is also called china jade. It is found in China and some other parts of Asia. The finest quality white jades can sell for up to $20,000 per kilo (2.2 pounds). Black jade is also found in China and is used for carving. Its color comes from iron oxide that has been introduced into the mineral during its formation. Blue jade is another type of Chinese jade. It contains selenite, which is also found in Brazil. Green jade is made up mostly of water and carbon dioxide when it first forms. As it ages, however, it absorbs oxygen from the air and becomes brown or black.