Jade is the name used to designate two different gemstones, the jadeite and the nephrite. It has been used as gemstone since ancient times, mainly in China. The Aztecs used it in the form of amulet and it was more appreciated than gold. Today, it is mainly used in the East.
Jade does not have transparency, therefore, it is cut into in the form of small sculptures. Jadeite is the rarest and most valuable of the two types of jade. It has a variable color i.e. white, violet, brown, orange-red or yellow, but mostly intense green due to chromium, sometimes with white spots. It ranges from semitransparent to almost opaque with vitreous to silky luster. It is mainly produced in Myanmar while other producers are China, Tibet, Japan, Guatemala and USA.
Nephrite is a variety of the mineral called actinolite. It is the most common and most resistant of the two types of jade. It is fibrous and translucent to opaque with vitreous luster. The most important one is the dark green nephrite, known as Chinese-jade. It is mainly used in ornamental objects and its lapidation requires a previous heating, followed by abrupt cooling.
The emerald is a variety of beryl, but with a greenish color, in a dark to medium tone. If it contains less than 0.1% chromium oxide, it is considered as a non-emerald beryl. It forms prismatic crystals of hexagonal base, but it is not transparent because it has countless fractures and fissures, and many of them are filled by impurities; only very small gemstones show very clear appearance. It is usually lapped in a faceted type itself, called emerald lapidation, in which the large facet is rectangular or square with the corners cut.
The earliest emerald mines emerged in Egypt, but there is no production in Egypt. It was already marketed two thousand years before Christ in Babylon, but it was rare until the time of the Renaissance when the South American deposits were discovered. Today, it is mainly produced in Colombia, Zambia, Zimbabwe, Tanzania, Madagascar and Brazil.
The emerald is one of the three most valuable gems, being the others ruby and the diamond, mainly because of its color. The best quality gemstones with 5 to 8 carats can be worth up to $5,600 per carat. Gems of the same weight with average quality range from $100 to $ 580 per carat. Emerald has been commercially synthesized since 1940. Unlike other minerals, the entire production of synthetic stones is for jewelry.