- Varieties and trade names of Jade
- Formation of Jade
- Sources and Recovery of Jade
- Jade Jewelry
- Physical & Optical Properties of Jadeite
- Physical & Optical Properties of Nephrite
- Test and Identification of Jade
In 1953 a sharp earthquake struck Southern U.S.A. In a small art shop there was chaos. The building itself was not badly damaged, but the stock of carved Chinese vases and other art objects had fallen to the floor. The carvings consisted of various chalcedonies, rose quartz, rock crystal, coral, beryl and jade, both nephrite and jadeite. The proprietors feared for their most valuable items, which were made of jade. Yet when they finally sorted out the tangle they were surprised and delighted to find that no one jade object had been damaged, even though the others had suffered in some degree from the fall. This was all the more surprising when it was realized that most of the more valuable objects were on the highest shelves. The jades were obviously tough.
This quality of toughness of the two minerals that we in the Western world refer to collectively as jade was well known to many prehistoric peoples. Archaeologists have shown that the superior toughness of jadeite and nephrite implements was appreciated by early peoples in widely separated areas. Functional articles were in use in Egypt between 4000 and 5000 B.C. Nephrite and some jadeite was used by prehistoric Europeans, particularly Swiss Lake Dwellers, for axe heads, scrapers and instruments of war. Prehistoric dwellers in China, too, used nephrite for implements, though there is evidence to indicate that jade's purely functional side began to diminish in the Chou Dynasty of recorded time (1722 B.C. to 206 A.D.), because carvings of esthetic and symbolic significance began to appear at about this time. At a much later date the Maori of New Zealand, carved their dark-green nephrite into articles of adornment, especially their "hei-tikis", which were used as heirlooms. These articles, which were usually in grotesque human forms, were sometimes buried with the dead. In addition, the Maori used nephrite for axes; in fact, their word for jade, "pounamu", means axe stone. Other prehistoric users of jade, mostly jadeite this time, were the peoples of Central America, including Guatemala and Mexico.
Most of the early peoples who made use of jade had not yet discovered the use of the harder metals for implements for everyday use. When these metals were discovered, some of the people mentioned above abandoned the use of jade entirely, such as the Swiss Lake Dwellers, whose use of jade stopped about 1500 B.C. Others transferred their affection for jade as a functional material to one of religious, symbolic or purely esthetic value. The great esteem in which jade is regarded is indicated by the fact that the Chinese word "yu" and the Japanese words "gyoku" and "tama" signify both jade and precious stones generally. A parallel exists in the Aztec language, in which the word "chalchihuitl" means both "jade" and "precious".
Our word jade is apparently derived from the last word of the name the Spanish Conquistadors gave to the jade they took by plunder in their visits to Mexico. The name "piedra de ijada" meaning "colic stone" was given to jade by the Spaniards when they observed the natives using it for its supposed efficacy in relieving the pain caused by kidney ailments. The name was first seen in print in 1569, when it was used by a Dr Monardes of Seville, Spain. In 1598 the term "ijada" appeared in English, In 1777 "jadde" appeared in English. In 1811 John Pinkerton, who coined the word gemology, wrote of "jad, the giada of the Italians". Early writers used Latin, and in Latin "piedra de ijada" was "lapis nephriticus", from the Greek "nephros" meaning "kidney". A. G. Werner of Freiburg, Germany, was the first (1789) to use the word nephrite in English. In 1863 Professor A. Damour, recognizing the difference between the two jades, coined the word jadeite.
"Lapis nephriticus" and "piedra de ijada" were more medical terms than mineralogical and they frequently referred to any stones, including jasper, green turquoise, serpentine, etc., which, upon trial, seemed effective in relieving pain associated with the groin. Early writers frequently called both jadeite and nephrite a variety of jasper. Marco Polo, visiting Turkestan in 1295, described the nephrite mines and called the stones "jasper". The real nature of nephrite and jadeite was made clear by Damour in 1863, when he separated the two species. Early people, who depended on the ability of jade to take and retain a sharp point and endure hard usage, were better able to identify substitutes than later people, who used the material for less functional purposes.
It is interesting to note that both the early Chinese and the people of Central America often buried bodies with jade objects. Frequently, a piece of carved jade was placed under the tongue. In China it was believed that powdered jade drunk before death would prevent decomposition of the body. In Central America, a bit of powdered jade taken occasionally (only by the wealth, of course) was felt to be a good tonic.
Prior to the introduction of jadeite from Burma into China in the middle of the eighteenth century, the esthetic use of nephrite was expressed mainly in articles with religious or symbolic meanings. These took the form of plaques, vases, screens; fingering pieces, statuettes, ring trays, paint-brush holders, triptychs, etc. With jadeite came a color never seen in nephrite: a bright, translucent, nearly emerald green that the Chinese compared with the kingfisher's plumes and called "fet's ui". This material occurred scantily in the boulders imported from Burma. Since it was scarce and beautiful, it came to be used for personal ornaments in the form of solid rings, buckles, carved pendants, earrings, buttons, necklaces and other articles. It is this color of jadeite that is most highly esteemed for jewelry in Western countries today.
Five of the many symbols used in Chinese jade carvings are illustrated on the accompanying plate. Figure 1 shows a dragon and a phoenix, both of which are symbols of strength. Figure 2 depicts the yin yang surrounded by the eight diagrams. Yang means positive, or male; yin means negative, or female. The eight diagrams are symbolic of the forces of nature. In Figure 3 the shou mark (the symbol of longevity) is surrounded by the five happiness's, or five blessings (symbolized by bats); i.e., old age, health; love of virtue, wealth and a natural death. The symbol of immortality, the butterfly, is illustrated in Figure 4. Figure 5 shows the mystic knot surmounted by the bat of happiness. The Chinese Buddhists revere the mystic knot as one of the auspicious signs found on the footprint of Buddha. The gourd, which is the symbol of magic, is shown in Figure 6.
The great reverence for jade, both as an article of personal adornment and in objects of art, is well illustrated by a description of the attitude of the Empress Dowager of China. Tzu Hsi, the last empress of China, was forced to flee in 1912 during the Boxer Rebellion. During her reign she valued jade beyond all other jewels. A story is told of her rejection of a fabulous diamond tiara offered by a favor seeker, but welcoming a visitor whose gift was a small but exquisite article made of Imperial green jade. It is reported that during her reign, and before; it was the custom for the jade dealers always to submit their finest jade to the Imperial Court for consideration. Since the court chose the finest translucent green available, the term "Imperial" jade become synonymous with this quality.
The Dowager Empress owned fabulous jade pieces. Her love of jade well illustrates the fact that no other gem material can be appreciated in so many forms and with so many senses: sight, sound and feel. The visual beauty of fine jade carvings and jewels goes without saying. The sensation of feel of polished jade is much appreciated, not only by the Chinese but by many others. The Empress had a favorite fingering piece of carved Imperial jade in the form of a small cucumber. The late Mr. G. Gump, noted Orient list and dealer in jade in San Francisco, was reputed to be able to determine the quality of polished jade by feel after he lost his eyesight.
The Dowager Empress frequently accompanied the palace orchestra with an instrument of her own made with twelve sets of gold bells and twelve sets of jade bells hung in carved wooden frames eight feet high by three feet wide. Gongs and wind bells of jade were employed in many Chinese households. This, again, emphasizes the quality of toughness no other stone could withstand such abuse.
Princess Der Ling, First Lady in waiting to Her Majesty, has published several books describing her life in the Imperial Court before its downfall. In many passages she has discussed the use of both jade Jewelry and jade utilitarian articles in the royal household. She is well qualified to discuss the Empress's jewels, since she was in charge of them- 3000 ebony boxes full! A painting of Her Majesty shows how greatly she loved jade. On her Manchu headdress are jewels of pearls and jade, cleverly wired so that each moved independently. On her shoulders she wears a cape like garment composed of more than 3000 pearls. Princess Der Ling tells us, "the size of a canary's egg." The cape ends in a fringe of magnificent jade drops. On the Empress's wrists are numerous solid jade bracelets. Rings of the finest green jade are on several fingers, and three inch jade fingernail protectors cover several fingers of both hands. It is reported that she used jade chopsticks and drank tea from exquisitely carved jade cups with gold saucers. Certain foods were eaten from carved jade plates. What other gem material could withstand being carved to such translucent thinness?
Travelers in Hong Kong today report that many Chinese residents, both native and refugee, prize a small piece of jade that they carry with them wherever they go.
It is of significance to note that long before jade was used for esthetic purposes, prehistoric people learned that pieces of maximum translucency and uniform texture were more apt to be enduring implements when carved. Perhaps early people worshipped the tools of jade that helped them to master their environment, and in transferring their affection from jade as a tool to jade as a symbol of religious or esthetic value, they established the many superstitions with which jade has been regarded. Did the Swiss Lake Dwellers cease to use jade because other materials supplanted jade and jade itself was no longer available, or was their jade not of sufficient inherent beauty to be regarded highly once its functional role had been fulfilled? Surely, most of the Lake Dwellers jade implements cannot be compared with the jade of China or even of Central America or New Zealand, from the standpoint of beauty alone.
Just what are these minerals that can be so functional and yet so beautiful and ornamental? Both jadeite and nephrite are crystalline aggregates occurring in massive form and composed of more or less fibrous, inter-grown crystals. This aggregate structure gives not only the exceptional toughness to these two minerals, toughness not matched by any other gem minerals, but also suggests why neither is ever absolutely transparent. Both may vary from opaque to translucent, although jadeite may occasionally be semitransparent. Another characteristic that can be partly attributed to the aggregate structure is that neither can easily be polished to a plane surface; thus, the luster is more properly described as greasy than vitreous. This seems especially true of jadeite.
In many qualities, jadeite and nephrite may resemble one another closely. Gray-green, white and grayish white with, streaks of dark green, as well as tones of brown to reddish brown to black, may occur in both minerals. Also, each may vary from opaque to translucent. However, the qualities valued for gemstones in Western countries are met most frequently in jadeite. This mineral occurs in an attractive, intense green that is unknown in nephrite. When this color occurs in a highly translucent stone, the specimen is very desirable and may command an exceptionally high price.
The terms "Imperial jade", "gem jade" or "emerald jade" are frequently used to describe an intense, emerald-green semitransparent chrome bearing jadeite. However, these terms are not universally accepted for the finest quality. Many people feel that "apple green" is the finest jade; i.e., medium yellowish green of high intensity. Perhaps personal preference accounts for the lack of agreement, but all will agree that these finest qualities are extremely rare.
A very dark green to black opaque variety of jadeite, called chloromelanite (pronounced klor-oh-MEL-an-ite), is effective in carvings and is found among the Swiss Lake Dwellers effects. It is but little valued as gemstone material and is consequently seldom seen by the jeweler.
Yellow or red-brown jadeite used as gemstones is seen only rarely. However, a light lavender ("mauve") jadeite is seen somewhat more often; it is not yet popular in western countries, being appreciated primarily by collectors and jade fanciers.
A rich-green jadeite, sometimes called "Yunan jade" though undoubtedly from Burma, may appear quite translucent when cut very thin. Worn in drop earrings, transmitted light shining through the stone may impart a strikingly rich color. In reflected light, unfortunately, it is not as colorful or valuable as the material that may be cut to produce some internal reflection. The color of fine jade has been described by some fanciers as penetrating, since it seems to be visible for greater distances when worn than similar green colors in other gem materials.
Nephrite (which, incidentally, is pronounced NEFF-rite) is not greatly used as a gemstone, though since the abundant find of nephrite in Wyoming, some very attractive dark grayish-green material with good translucency has been seen in jewelry. At best, it does not approach the desirability and beauty of the better greens found in jadeite. The very finest New Zealand jade (nephrite), sometimes called "New Zealand greenstone" or "spinach jade" is often considered quite attractive but it does not command a high price; its color is darker and more grayish green, which does not suggest emerald.
To the Chinese, translucent white to yellowish-white mutton-fat jade is highly desirable as well as mottled white with green "streamers" called "moss-in-snow" jade. Jade implements and ornaments of all kinds are carved with symbolic figures, such as the lotus blossom, peach blossom, "fungus of life" the "mystic knot" and the bat. The latter, which signifies happiness, is actually a pun in Chinese, since the word for bat and happiness are the same.
Formation of Jadeite
Jadeite is a silicate of sodium and aluminum, with the chemical formula expressed as NaAl(SiO3)2. It is a mineral of the pyroxene group of rock-building minerals and is therefore related to such single-crystal gem minerals as spodumene (kunzite, hiddenite), diopside and enstatite. When pure, jadeite is white; but when it contains varying amounts of different oxides, particularly ferrous and ferric oxides, various gray-greens, yellow-greens, reddish-browns, yellows and grays may result, as well as the rarer lavender, or mauve, jadeite. The finest greens are caused by the incorporation of chromic oxide in the structure, the same impurity that is responsible for the color of emerald.
The geological origin of jadeite has yet to be established definitely. It formed perhaps as a result of metamorphism of igneous rocks at a great depth below the surface. At the mines near Tawmaw, Burma, about 65 miles from Mogaung, there is a very thick overburden of red earth, probably from the weathering of serpentinized peridotites that formed the rocks into which the jadeite-albite mass is intrusive. Below the serpentinized peridotites lies a thin, earthy, very light schist. Next are two layers of igneous rock overlying the jadeite-bearing rock.
Formation of Nephrite
Nephrite is a hydrous silicate of calcium and magnesium, for which the formula is CaMg5(OH)2(Si4O11)2. It is a member of the tremolite-actinolite series of the amphibole group of rock-forming minerals. Tremolite tends to be white or grayish and actinolite encompasses the darker green colors, due to the varying amounts of ferrous oxide. Oxidation of the ferrous iron to ferric iron, especially along cracks and in more or less porous and exposed sections of the "skin" of a specimen, produces a red-brown color. A true red probably never occurs in either jadeite or nephrite, though it does occur in several minerals that have been offered as jade. Gray nephrite is occasionally seen, the color of which seems to be produced by numerous inclusions of actinolite or tiny hornblende crystals in a whitish material. Black nephrite is usually an exceedingly dark-green material, which can be seen if a specimen is held over a strong light source and observed in the thinner edges. Rarely, the arrangement of actinolite fibers is sufficiently oriented to enable a cat's-eye effect to be seen when the stone is cut in cabochon. This effect has not been reported in cut jadeite, probably because the crystals do not tend to be so fibrous in jadeite.
Sources of Jadeite
Jadeite first became known to the Chinese in the middle of the eighteenth century, according to the best information available; all older Chinese jade pieces are nephrite. Now as then, the source of this jadeite is upper Burma, within an eighty-mile radius of the town of Mogaung, which is very near the Yunan Province of Red China. Both alluvial boulders and jadeite in situ have been taken from the area.
The mining methods used today are still the same essentially as those used hundreds of years ago, except that hydraulic drills are now employed in areas and the wasteful practice of heating large boulders and shattering them with water is seldom used. Jade mining progresses for only three months, from March to May, because of the rainy season, when the shafts quickly fill with water.
Before any jade mining is begun, every worker, whether Kachin, Shan, Burman or Chinese, prays to the jade spirit, or "Nats", in the belief that they will discover valuable jade quickly if the nats are pleased. Generally, the over burden is quarried with picks and crowbars until a steep face is obtained. Water is dammed upstream to make it flow over the steep face washing away all earth and leaving the boulders clearly exposed for examination. It is well to remember that the selection of the locality and all the workings are started through pure instinct: inner conviction of the miners, rather than any sound scientific reasoning directs them. When a valuable strike is made, the miners flock to the spot and work it until all the jade has been removed. Consequently, they frequently forget where they worked last and begin digging in places previously mined, with much labor thus lost. Scientific, well organized mining would undoubtedly yield larger amounts of fine jade at a fraction of the present cost to the jade merchants, who do almost all the financing.
Boulders found in the mines are evaluated and local taxes assessed before they are transported to Mogaung, the principal trading center. There the Government collects 33% of the value before the merchants are fallowed to ship it out of Burma. The value at this point is fictitious, the idea being to keep the appraisal low until all taxes are paid. The jadeite boulders are prepared for local auctions and for export as follows: Each one is weighed and a seal is placed on it. At strategic points, each boulder is "mawed": that is, cuts of about three-fourths of an inch in width and one-half inch in depth are made with the edge of a grinding wheel and then polished. This exposes the interior for better, though still speculative examination. Buyers are actually gamblers, though the Chinese merchants pride themselves on their ability to evaluate each boulder on the basis of the polished cuts. The boulders are wrapped in heavy sailcloth and bound with hemp rope before they are shipped down the Irrawaddy River to Rangoon and thence to Hong Kong. A considerable quantity is smuggled across the border into Yunan, Communist China. About 15% of the boulders, mostly the poorest quality, remains in Burma and is usually sold in Mandalay to be cut and set into jewelry.
The discoveries of jadeite in other parts of the world are mainly of scientific interest, since none has given promise of providing really fine-quality material. One source, only recently reported, is near the village of Manzanal, in the Motaqual Valley of Guatemala. Until this discovery, the Central American. Source of jadeite was a mystery, although it was long known by the pre-Spanish residents of Mexico and Guatemala. Some of the material is quite acceptable for modem jewelry. The deposit has yet to be commercially exploited. Unlike the Burmese jadeite, this material is a diopside jadeite, rather than a soda jadeite; that is, it contains considerable calcium and magnesium, in addition to the usual sodium and aluminum.
In Japan, specimens of jadeite have been discovered near the village of Katakl, Niigata Prefecture, in association With albite and quartz. For the most part, it is not satisfactory for cutting, since it contains soft streaks of included tremolite and albite and the color is usually poor. A large specimen submitted to the USA National Museum in Washington was repeatedly sliced until only a small, very light-green slice with included dark actinolite crystals was left the only part considered worthy of display. The American Museum of Natural History displays an attractive opaque light-green statuette of Kuan Yin, the Chinese Goddess of Mercy. Beads presented to the GIA's Gem Trade Laboratory in New York as "Japanese jadeite" proved to be albite, prehnite and an albite-actinolite mixture. No jade was encountered among the sixty beads.
Sources of Nephrite
Turkestan (Sinkiang Province of China).For centuries, up until the present day, the most important source of nephrite to the Chinese has been the province of Sinkiang (Chinese Turkestan). The mines are located on the north slopes of the Kuen-Iun Mountains, fringing the Tarim Basin. The nephrite is said to occur in a layer of from twenty to forty feet thick between hornblende schist and gneiss. The layer of nephrite extends for miles along the mountain slopes, but the material is worked today largely in the beds of the Karakash, Yurangkash and Keriya Rivers, where the original deposit has been reduced to alluvial boulders. In earlier days, the original deposit was worked. The present, most important centers of mining are the cities of Hotien and Yutien. In 1880 a less important deposit of nephrite was found in the Pamir district further west in the same province, as was to be expected from the occurrence of nephrite pebbles found earlier in the streams of the region. Other deposits have been reported in China, but they have not been substantiated. The nephrite from Sinkiang Province is generally lighter in tone than that found elsewhere, though material has been found in all colors for which nephrite is known.
U.S.S.R.Another important nephrite source lies south of Irkutsk in the Lake Baikal region of Siberia (U .S .S .R .). The material occurs in boulders that have probably been carried down from the Sayan Mountains and deposited in the beds of the Bielaya, Kitot, Bistraya, Sludyanka and Onot Rivers. It is undoubtedly nephrite from this source that was used by the famous Russian jeweler, Faberge, for his wonderful carvings.
New ZealandNephrite is found in New Zealand in the northern part of Westland on South Island. It occurs as pebbles and boulders in the glacial debris in the valleys of the region near Kumara , Nephrite has also been found in place in talc and talc-serpentine rocks of the Griffin Range. It is most often some tone of green, grading into black. In the U.S. National Museum in Washington is a large boulder of New Zealand jade that has been sliced and polished. One thin slice displayed with transmitted light reveals a handsome green color. A boulder weighing more than 7000 pounds has been displayed at the American Museum of Natural History since 1902. It was formerly the base for a life-size statue of a Maori warrior.
United StatesPerhaps the most important source of nephrite to the International market since 1940 is the area near Lander, Wyoming. Here it has been found in all qualities, though most often in shades of green. Some boulders consist of nephrite, gray zoisite and pink thulite integrown with dark crystals of hornblende. Before this pink-and-gray material was identified, it was offered as "pink jade". Large specimens have been found from which carvings weighing more than one hundred pounds have been made. Notable among these is the sculpture "Thunder" by Donal Hord, which weighs more than one hundred forty-five pounds and is a uniform, translucent green. Much material from Wyoming has been tumbled for inexpensive jewelry. Much of the production consists of poorly textured and mottled nephrite, but specimens have been found that match the best that New Zealand has produced. Although some material has been found in place, most of it has been recovered as "float". One firm has mined and shipped many hundreds of pounds to its distributor in New Jersey.
AlaskaEskimos along the Pacific Coast of North America made considerable use of nephrite, and early explorers noted the many tools in use made of the green stone. When it was identified as nephrite, a theory was advanced about migrations of jade traders from Siberia, since no American source of nephrite was known. However, in 1885, nephrite was discovered in place in Alaska about 175 miles from the mouth of the Kobuk River near a stream called Shungnak, the native name for jade. The nephrite is associated with serpentine, asbestos (both chrysotile and tremolite), magnesite, antigorite and magnetite. The deposit covers a wide area, though much of the material is scaly, opaque and unfit for cutting. Boulders in the river beds are of much better cutting quality, because nature has performed the grading and sorting by removing the scaly, low-quality material. Because of the remote location of the Alaskan source of nephrite, the supply has been little exploited.
British ColumbiaAbout the same time that nephrite was discovered in Alaska, it was found along the Fraser River in British Columbia. The actual geological source has not been discovered, but it is still possible to find pebbles and boulders in the sandbars, along the shores, and among the placer gold-mining debris left from gold-rush days. As with jade deposits the world over, a very small percentage of the material is considered to be gem quality or even worth cutting.
SilesiaIn 1884 an original source of nephrite was discovered in Silesia, near the town of Jordansmuhl, an area that is now in Poland. The finding of a European source of nephrite partially explains the source of the nephrite axes and other implements used by various early Europeans, particularly the Swiss Lake Dwellers. However, the source of the jadeite implements has not been discovered. The Silesian source has never been important commercially, although Dr. George F. Kunz, the noted gem authority and author, found a 4718-pound boulder there; it has been displayed in the Mineral Department of the American Museum of Natural History in New York since 1899.
TaiwanWhile on a buying trip to Taiwan (Formosa) in 1965, an American colored stone dealer was offered a quantity of attractive green cabochons cut from material found on the island near the town of Hua-lien. The next day he visited the source, an asbestos mining area outside of Hua-lien, collected specimens of the green material and returned to the United States. Samples sent to the GIA laboratory in Los Angeles were tested and proved to be nephrite. Since then Taiwan has been a steady producer of nephrite.
Minor SourcesMinor nephrite deposits have been reported on the Island of New Guinea, north of Australia, and Wen Island, off New Caledonia. Very little information is available about the deposits and it is assumed that they lack promise.
The modem lapidary, accustomed to electrical power, diamond saws and fast cutting and polishing wheels, find the methods used in China and Hong Kong almost unbelievably crude. That these tough jade minerals are worked into such intricate designs, carved to egg-shell thicknesses, and given such a beautiful polish does seem almost impossible with their rudimentary equipment.
Small cuts are made with soft iron discs driven by foot-powdered lathes. These lathes consist of a spindle around which a leather strap is wound. Each depression of the foot pedal reverses the rotation of the lathe. Drilling and piercing is done by the use of a simple bow drill and carborundum powder in water. Nephrite is polished against discs of thick ground rind cemented to the ends of the lathe spindle. The agents used for polishing are native iron oxides. Fine polishing for gems of jadeite is done on composition wheels made of glue, resin, linseed oil and iron oxide (rough). Large or very delicate pieces are normally suspended over the lathe from a line through a pulley and balanced by a counterweight. By this method extremely thin “egg-shell” carving can be made in the form of bowls, vase and cups. Jadeite particularly is adaptable to the latter forms because of its translucency. The Chinese have long been adept at incorporating spots of color and the natural mottling of the "skin" of the boulder into their works of art.
Modern western lapidaries fashion jadeite and nephrite into a variety of forms, some of which because of jade’s great toughness, are never used for any other gem material. For instance, solid “hololith” rings and bracelets are quite popular, even they cannot be sized. Perhaps the most popular form for fine jadeite is the oval, double cabochon cut, though all shapes of cabochons are used. Less transparent and mottled material, both is frequently carved and pierced and used as buttons or as sets for bracelets and necklaces. Drops are popular, both carved and uncarved. Graduated color blended jadeite beads have long been popular. Some of the most expensive jade jewelry sold consists of translucent to semitransparent intense green beads strung in necklaces. Linked chains and flat pierced discs are sometimes worked into clever designs or gold jewelry. Nephrite of American origin is frequently tumbled, resulting in highly polished baroque and free from shapes. Very rarely, an almost transparent fine jadeite is faceted.
The fashioning of jadeite and nephrite presents a number of unique problems, primarily because of the random orientation of the minute crystals. As a result of this structural characteristic, undercutting sometimes occurs during the sanding operation, producing a grainy or "dimpled" appearance on the surface. Satisfactory results can usually be obtained, however, by using a well worn sander at a fairly low speed or a wet sander with a continual flow of water.
Depending on the structural quality of the material and the technique of the operator, one of several polishing methods may produce the desired results. One method is to use a dry, hard-felt lap with heavy pressure and low speed. This must be done with the utmost care, however, since the heat thus generated may soften the wax and loosen the stone on the dop. Some lapidaries prefer a leather (cowhide) lap with chromic oxide and a small amount of oxalic acid to dissolve any iron stains that may be present. Other methods involve the use of a soft wooden lap with tin oxide or a cowhide lap with "Linde A" as the polishing agent. Very compact material may lose its characteristic "soft" luster and appear somewhat like chalcedony, which is noted for the excellent polish it takes. Many jade fanciers believe that some of the charm associated with jade is lost by this ultrafine polish.
|Chemical Composition||A silicate of sodium and aluminium, expressed by the formula NaAl(SiO3)2|
|Crystallographic Character||A granular to fibrous crystalline aggregate; compact and massive. Monoclinic system of crystallization.|
|Hardness||6½ to 7|
|Cleavage||Not visible because of its aggregate structure.|
|Fracture||Fine granular to splintery.|
|Specific Gravity||3.30 to 3.38; normal: 3.34|
|Degree of Transparency||Semitransparent to opaque.|
|Luster||Polished surfaces are vitreous to greasy; fracture surfaces are dull.|
|Refractive Index||1.66 - 1.68. Because of its aggregate structure, only rarely are two readings visible; usually a single reading at 1.66 is seen.|
|Birefringence||0.020; not usually measurable on a cut stone|
|Optic Character||Biaxial positive, but not possible to determine by usual gem-testing methods. Translucent stones remain light in the polariscope.|
|Pleochroism||Usually not evident because of its aggregate structure.|
|X-Ray, Fluorescence||Most pale colors are white or yellowish white. However, colorless, light-yellow and light-mauve stones often exhibit a strong violet or blue-violet color.|
|Transparency to X-Rays||Semitransparent|
|Ultraviolet Fluorescence||None to very weak whitish, greenish or yellowish under long wavelength.|
|Color-Filler Reaction||A weak, low-intensity red on some dyed material.|
|Absorption Spectra||Translucent stones, if not too dark, usually show a line at 4370 A.U. Chrome-green stones usually-show three lines in the red at 6915, 6550 and 6300 A.U. Stones treated with green dye show only a single, broad band in the area occupied by the three chrome bands in the untreated material.|
Effects Caused by:
|Heat||Fuses easily to a blebby glass (i.e. forming bubbles) when exposed to the blowpipe or Bunsen burner.|
|Acids||Slightly affected by warm acids.|
|Chemical Composition||A hydrous silicate of calcium and magnesium; expressed by the formula CaMg5(OH)2(Si4O11)2|
|Crystallographic Character||A fibrous crystalline aggregate; compact and massive. Monoclinic system of crystallization.|
|Hardness||6 to 6½|
|Toughness||Exceptional; outranks jadeite|
|Cleavage||Not visible because of its aggregate structure.|
|Fracture||Fine granular to splintery.|
|Specific Gravity||2.90 to 3.30; normal: 2.95|
|Degree of Transparency||Semitransparent to opaque.|
|Luster||Polished surfaces are vitreous to greasy; fracture surfaces are dull.|
|Refractive Index||1.606-1.632. Because of its aggregate structure, only rarely are two readings visible; usually a single reading at 1.61 is seen.|
|Birefringence||0.026; not usually measurable on a cut stone|
|Optic Character||Biaxial negative, but not possible to determine by usual gem-testing methods. Translucent stones remain light in the polariscope.|
|Pleochroism||Usually not evident because of its aggregate structure.|
|Transparency to X-Rays||Translucent|
|Absorption Spectra||Rarely shows any absorption lines. If fibers of actinolite are present, a vague line may be visible at 5000 A.U. Vague chromium lines may rarely be seen in green stones of exceptional quality.|
Effects Caused by:
|Heat||Not affected by Bunsen burner, but fuses slowly in blowpipe flame|
|Acids||Slightly affected by warm acids.|
The distinction between jadeite nephrite based on gemological tests is usually not difficult, if the stone to be tested is polished. The difference in refractive index alone is enough so that no confusion should result. If the piece is small and not set, a specific gravity test will separate the two. Jadeite frequently has almost the same slowly, may remain suspended is rarely, come slowly to the surface. A hardness test is of little value, since the two minerals are very similar in this respect. The presence of an absorption line at 4370 A.U. in jadeite is very helpful, particularly when dealing large carvings that are not well polished. An intense, nearly Emerald green color is typical of jadeite rather than nephrite.
A few years after detection of the dyed jadeite cabochons in 1956, jadeite triplets were identified, the color and quality of which was even finer than the dyed stones. The jadeite triplets are cunningly constructed by making a very thin hollow cabochon of translucent grayish-white jadeite. A solid cabochon that fits snugly into the concavity of the outer hollowed cabochon is coated with green jellylike substance that resembles, both in appearance and consistency mint jelly. It is placed in the hollowed cabochon and a piece of flat, oval jade is cemented to the bottom to complete the stone. Loose and un-mounted, the deception is evident. Set in rings, earrings and cufflinks with covered backs or heavy bezels, the separation plane is invisible. These stones, which are better in translucency than the dyed stones, have been pawned and sold for large sums of money. The detection of mounted triplets can sometimes be effected by observing bubbles and separations in the green jellylike filling, if the hollowed cabochon is think enough. The spectroscope shows the same broad absorption band in the red that is typical of the green-dyed stones. Though attractive when first assembled, the triplets pleasing appearance is not permanent. In time, the green jellylike substance dries out, or leaks out, causing discoloration.
The Chinese have long polished other minerals than jadeite and nephrite and sold them as jade. It is their belief that softer minerals are just jade in "infant" stages. As jade has become more popular in western countries as a jewelry stone, many opaque to semitransparent stones have been placed on the market that resemble jade of some quality. Since the public is not well acquainted with jade, the sale of inferior substitutes does nothing to enhance its importance. The accompanying chart includes those minerals and imitations that may either be mistaken for nephrite or jadeite or that have been sold as jade. Although the chart may seem long and perhaps too exhaustive, it does serve as a reminder that many materials have been mistaken for the jades, because they occur in many qualities and colors. Most of the stones listed occur in a green color or are dyed green to imitate the best quality of jadeite. Those that do not occur in a green color probably resemble stones seen in carvings and art objects, rather than gemstones. It has been the experience of the GIA staff that the following most closely approach the so-called Imperial-green color: green grossularite garnet, dyed serpentine, smithsonite, emerald, glass and enamel on metal, and dyed calcite, in addition to the dyed jadeite and jadeite triplets mentioned above.
In addition to the materials on the chart, there are others that may sometime's resemble jadeite or nephrite. Among those are wollastonite, a soft, whitish mineral; pyrophyllite, a soft, soapstone like mineral; smaragdite, an opaque to semi-opaque dark-green alteration product; and others, most of which are soft and seen mainly in carvings rather than in jewelry. Some alteration products of other members of the groups to which jadeite and nephrite belong may resemble jade, in which case gemological testing methods may not be adequate and X-ray and petrographic tests will be required.
Nearly all the materials on the chart can be distinguished from nephrite and jadeite by a combination of R.I., S.G. and, occasionally, hardness, together with observation of broken surfaces. Gray-green prehnite has properties very much like those of nephrite, but one who is familiar with nephrite will recognize prehnite's greater transparency. On the other hand, the enamel like white prehnite from Japan appears too opaque. It is possible that more specialized mineralogical testing methods may be required to separate this material from nephrite. Note that polariscope reactions have been omitted from the chart, because most jade substitutes as well as the jades themselves, give the same reaction; i.e., they remain light when rotated in the instrument.
The identification of jade comprises one of the most frequent requests of the Laboratories. On one occasion, the sale of a necklace of graduated beads of fine color, very translucent and evenly textured, depended on a certificate from the Laboratory. The price offered in the trade, if they proved to be jadeite, was Rs.1,60,000. A refractive index and specific gravity test, together with microscopic examination, were enough to determine that the beads were dyed serpentine. The owner was so sure that he had jade that he had an expensive X-ray diffraction and thin section analysis made by a university laboratory, which substantiated the GIA's identification. Needless to say, in spite of the great beauty of the material, the necklace brought nothing like the Rs.1,60,000 figure. In fact, he finally disposed of it for less than the sum of his testing fees.