Jade is an ornamental stone. The term jade is applied to two different metamorphic rocks that are made up of different silicate minerals. Jade refers to two different minerals—jadeite and nephrite.
Nephrite consists of a microcrystaline interlocking fibrous matrix of the calcium, magnesium-iron rich amphibole mineral series tremolite (calcium-magnesium)-ferroactinolite (calcium-magnesium-iron). The middle member of this series with an intermediate composition is called actinolite (the silky fibrous mineral form is one form of asbestos). The higher the iron content the greener the colour.
Jadeite is a sodium- and aluminium-rich pyroxene. The gem form of the mineral is a microcrystaline interlocking crystal matrix.
Both stones are rocks (aggregates) -- masses of tightly interlocking crystals. However, they have different chemical composition and properties. Jadeite is a little harder and denser, and as result can take a higher polish than nephrite. Neither stone is very hard, compared to diamond and ruby. However, both jades are unusually tough—resistant to breakage and chipping. Nephrite, however, is slightly stronger.
Jadeite is more valuable and rare than nephrite. When it’s very translucent and has a strong emerald-green color, it’s often called imperial jade. Jadeite is found in a variety of colors—lavender, white, gray, yellow, orange, brownish—red, black and many shades of green. Today, jadeite is usually the jade chosen for fine jewelry. Its intrinsic value is generally the basis for its price. Nephrite, on the other hand, is mainly valued for its antiquity and carving excellence.
Nephrite is plentiful and most of it is grayish green—typically forest green or olive green. It can also be white, gray, black, brown, yellow, or beige. Most nephrite is very affordable. For example, you can easily find nephrite costume jewelry ranging from $10 to $50. The antique value of old nephrite pieces often outweighs their intrinsic worth.
Many minerals are sold as jade. Some of these are: serpentine (also bowenite), carnelian, aventurine quartz, glass, grossularite, Vesuvianite, soapstone (and other steatites such as shoushan stone) and recently, Australian chrysoprase. "Korean jade," "Suzhou jade," "Styrian jade," "Olive jade", and "New jade" are all really serpentine; "Transvaal jade" or "African jade" is grossularite; "Peace jade" is a mixture of serpentine, stichtite, and quartz; "Mountain jade" is dyed dolomite marble.
Evaluation and Identification of Jade Jewelry: Fake or Genuine?
COLOR: An intense green with a medium-to-medium—dark tone is most valued. As the color becomes lighter, darker, more grayish or brownish or yellowish, the value decreases. Lavender is the next most valued hue, followed by red and yellow, white and black. Prior to the importation of Burmese jadeite into china, white nephrite was the most coveted jade.
Green nephrite is typically grayish, blackish, or brownish. The more it approaches a pure green, the more desirable it is.
COLOR UNIFORMITY: In top quality jade, the color is uniform throughout the stone. The more uneven or blotchy the color is, the lower the value. Multi-colored jade, however, can be very expensive if the colors are intense and distinct. The most desired color combinations are green and lavender, arrange and green, or white with strong green (moss-in-snow jade).
TRANSPARENCY: The best jade is near either transparent or highly translucent. As the transparency of jade decrease, so does its value, with opaque jade being worth the least.
CLARITY: Fine jade is free of flaws such as cracks, included foreign material, and spots which reduce beauty or durability. The number, size, color, position, and nature of flaws determine the clarity of stone. Cracks that break the surface or that are visible internally are particularly detrimental to the value.
TEXTURE: Since jade is composed of interwoven crystal, it can have texture that ranges from fine to coarse. The finer and more tightly interwoven the crystal components are, the better the jade.
SHAPE: The best jade is cut into cabochons. Ovals and rounds normally sell for more than rectangular, marquise and pear shapes. Smooth uncarved pieces are more valuable than carved ones. Carving allows the removal of flaws from inferior material.
CUT QUALITY: Moderately curved cabochons tend to be more valued than flat or very high ones. Symmetrically cabochons with balanced proportions are the most desired. Intricate, high-quality carving is naturally more valued than shoddy, quick carving.
SIZE: Since large, fine quality jadeite is rare, size plays a role in increasing its value. The thickness of good jadeite is also important. If a jadeite cabochon is thinner than 2 mm or smaller than 8 x 6 mm, there can be considerable deduction in its per-carat value.
POLISH & FINISH: The more brilliant the polish and the smoother the surface, the better the stone is.
Treatments of Jade Jewelry
Waxing: This is commonly done after the final polish to improve luster and hide pits and cracks. Heat and strong solvents will undo this treatment. Material will only a superficial waxing is often called A Jade and is well-accepted by the trade.
Dyeing: This is done to add green or lavender color to white or light-colored jade. Blueberry juice is a common dye for lavender jade. It looks good at first but it can fade in sunlight. Dyed jade is called C Jade and is not accepted as fine jade.
Heating: Dark green nephrite may be treated by this method to lighten the color of dark-green material. Red jade can be heated to increase redness, but the usual result is a dull brown, and transparency is reduced in the process.
Bleaching and polymer impregnation: This relatively new treatment removes brown from jade, making whiter colors whiter and green colors brighter. The jade is first soaked and bleached in chemicals. Then the bleached jade is impregnated with a wax or synthetic resin to fill voids created from the bleaching process. The resulting material is called B Jade. Sometimes dye is used before impregnation and other times it’s added to the filter. Don’t plan on handling bleached jade down to future generations; it has durability problems and will discolor with time.
Major sources: Myanmar has been the main source of jadeite since the late 18th century. Some jadeite is also mined in Russia, Japan, California; but the finest quality comes from Myanmar.
The oldest known source of nephrite is Xinjiang Province in China. Nephrite is also found in New Zealand, Taiwan, British, Columbia, Australia, Poland, Germany, India, Zimbabwe, Mexico, Alaska, California and Wyoming.
BEWARE: Sellers are supposed to disclose treatments but not all do. Therefore ask for treatment information, particularly when buying high-priced jadeite. If a store claims their jade is only waxed and otherwise untreated, have them write this on the receipt. If you’re buying quality jade jewelry, check if it has open back setting to let it light through the stone. Closed backs are typically a sign that the jade is of low value or that something is being hidden. For example, it might be hiding the back of a jadeite triplet—an assembled stone consisting of a thin hollow cabochon of translucent grayish-white jadeite that’s coated inside with a thin, green jelly-like substance and cemented to a piece of flat oval jade. When mounted it looks like an imperial jadeite cabochon. You’re much more likely to encounter dyed jade, than jadeite triplets.
Some common jade imitations are serpentine, chrysoprase, glossular garnet and dyed chalcedomy.
Care tips: Jade can be safely cleaned in soapy water, ultrasonics and steamers. It reacts slightly to warm acids. Since jade has a lower hardness than gems such as sapphire, emerald, and topaz, it can be scratched more easily. Jewelers can eliminate the scratches and restore the luster by polishing the jade.
Jade, however, is very durable. In fact, there is no other gem that’s as resistant to breakage and chipping as jade.
Enhancement of Jade Jewelry
Jade may be enhanced (sometimes called "stabilized"). Note that some merchants will refer to these as Grades, but it is important to bear in mind that degree of enhancement is different from colour and texture quality. In other words, Type A jadeite is not enhanced but can have poor colour and texture. There are three main methods of enhancement, sometimes referred to as the ABC Treatment System:
1) Type A jadeite has not been treated in any way except surface waxing.
2) Type B treatment involves exposing a promising but stained piece of jadeite to chemical bleaches and/or acids and impregnating it with a clear polymer resin. This results in a significant improvement of transparency and colour of the material. Currently, infrared spectroscopy is the most accurate test for the detection of polymer in jadeite.
3) Type C jade has been artificially stained or dyed. The red colour of Red jade can be enhanced with heat. The effects are somewhat uncontrollable and may result in a dull brown. In any case, translucency is usually lost.
4) B+C jade is a combination of B and C: it has been both artificially dyed AND impregnated.
5) Type D jade refers to a composite stone such as a doublet comprising a jade top with a plastic backing.
---how to identify jade jewelry (jadeite & nephrite)
5:46 PM | Buying Guide, Gems Identification, Gemstone Treatments, Jewelry Care Tips with 0 comments »