What is Jade?
Jadeite and nephrite are materials that have both been called "jade" for thousands of years.
What is Jade?
"Jade" is a cultural term used for a very durable, and often beautiful, material that has been fashioned into tools, sculptures, jewelry, gemstones, and other objects for over 5,000 years. It was first used to manufacture ax heads, weapons, and tools for scraping and hammering because of its toughness.
Then, because some specimens had a beautiful color and could be polished to a brilliant luster, people started to use jade for gemstones, talismans, and ornamental objects. Although most people who think of jade imagine a beautiful green gemstone, the material occurs in a wide variety of colors that include green, white, lavender, yellow, blue, black, red, orange, and gray.
Are All Jades the Same?
Originally, all jade objects were thought to be made from the same material. However, in 1863 a Frenchman, Alexis Damour, discovered that the material known as "jade" could be divided into two different minerals: jadeite and nephrite.
Because these two materials can be difficult to distinguish, and because the word "jade" is so entrenched in common language, the name "jade" is still widely used across many societies, industries, and academic disciplines.
In this article, the word "jade" will be used for undifferentiated materials. "Jadeite" or "nephrite" will be used when the identity of the material is known. The word "nephrite" is also an imprecise term. It is used for materials composed of the minerals actinolite and tremolite.
Physical Properties: Jadeite and Nephrite
|Silicate - pyroxene.||Silicate - amphibole.|
|Usually various shades of white to dark green, sometimes gray, pink, lilac, red, blue, yellow, orange, black, colored by impurities.||Usually ranges in color between white, cream, and dark green.|
|Vitreous to sugary.||Vitreous to silky, waxy.|
|Translucent to opaque.||Translucent to opaque.|
|Usually not seen because of a small grain size and splintery fracture.||Prismatic but usually not seen because of a small grain size and splintery fracture.|
|6.5 to 7||5 to 6|
|3.3 to 3.5||3.0 to 3.3|
|Color, toughness, hardness, specific gravity, grain size and habit.||Color, toughness, hardness, specific gravity, grain size and habit.|
|NaAlSi2O6 or Na(Al,Fe3+)Si2O6||Ca2(Mg,Fe)5Si8O22(OH)2|
|Jewelry, ornaments, tools, weapons, gemstones.||Jewelry, ornaments, tools, weapons, gemstones.|
Jadeite, Nephrite, and Science
Jadeite and nephrite have distinctly different mineral compositions. Jadeite is an aluminum-rich pyroxene, while nephrite is a magnesium-rich amphibole. However, the two minerals have very similar physical properties in the eye of the average person. Only trained observers with significant experience are able to reliably differentiate them without mineral testing equipment. This is why jadeite and nephrite were not properly distinguished by scientists until 1863.
Jadeite, Nephrite, and Artisans
China has been the leading producer of jade objects for over 5,000 years. A few hundred years ago, master Chinese craftsmen who worked with jade daily recognized that some of the jade obtained from Burma (now the Union of Myanmar) was different. It was harder, denser, worked easier, and produced a higher luster upon polishing. It gradually became the form of jade preferred by Chinese artisans and the jade most highly prized by the Chinese people. They realized this long before scientists differentiated jadeite and nephrite in 1863.
Unknowingly, Chinese craftsmen had distinguished jadeite from nephrite and appreciated it enough to pay premium prices for jadeite. However, they didn't have the knowledge and equipment of chemistry and crystallography to distinguish them in a formal way.
Rarely, the Chinese craftsmen encountered fine-grained jadeite with a bright translucence and a rich, uniform green color. This beautiful material was given the name "Imperial Jade" and regarded as the stone of highest quality. At that time in China, ownership of Imperial Jade was reserved only for the Emperor. Now, anyone who can afford it can own Imperial Jade. The best specimens can cost more per carat than high-quality diamonds.
Waxes, dyes, bleaches, polymer impregnation, heat treatments, and other procedures are sometimes used to improve the color and luster of jadeite and nephrite to give them the appearance of the finest jade. These treatments can usually be detected in a careful examination by an experienced person using a microscope, hand lens, and ultraviolet light. An untrained person is unable to recognize most of these treatments. Sellers have an ethical obligation to accurately identify the material that they are selling and reveal any treatment that has been applied.
The caution to buyers is this: If you are spending serious money for a jade object, be sure that you are buying from a knowledgeable and trusted dealer. If you don't know what you are buying, then you should pay no more for jade than you would pay for the same object made from a material with no intrinsic value.
Early Use of Jade in Tools
People have used jade for at least 100,000 years. The earliest objects made from jade were tools. Jade is a very hard material and is used as a tool because it is extremely tough and breaks to form sharp edges.
Most jade does not have a color and translucence that is expected in a gemstone. However, when early people found these special pieces of jade, they were often inspired into crafting them into a special object.
"Toughness" is the ability of a material to resist fracturing when subjected to stress. "Hardness" is the ability of a material to resist abrasion. Early toolmakers took advantage of these properties of jade and formed it into cutting tools and weapons. It was used to make axes, projectile points, knives, scrapers, and other sharp objects for cutting.
Use of Jade as a Gemstone
Jade is a durable, colorful material that can be worked into shapes and given a high polish. These properties make it a very desirable gemstone. Jade has been used to make a variety of jewelry items such as pendants, necklaces, rings, bracelets, earrings, beads, cabochons, tumbled stones, and other items.
These jewelry items are often made of solid jade, combined with other gems, or placed in settings made from gold, silver, or other precious metals. In addition to jewelry, jade is used to make small sculptures, ornaments, religious art, and small functional objects.
Other Materials Confused With Jade
A number of other minerals and materials that are commonly cut and polished are easily confused with jade. All of these materials can have a color, luster, and translucence that is very similar to jade - so similar that the average person is unable to recognize them. These materials are often used to manufacture cabochons, beads, and other objects in the same style as jade. They sometimes enter the jade market without distinction.
Chalcedony is a translucent variety of microcrystalline quartz that occurs in a range of colors similar to jade. Chrysoprase is a bright green chalcedony colored by chromium that, when cut into cabochons, beads, and small sculptures, will look very similar to jade. Chalcedony occurs in a variety of other translucent colors such as black, lavender, yellow, and orange that can look like the color varieties of jade. Chalcedony can be a very close gemstone look-alike with jade. It can be differentiated from jade using is lower specific gravity and by a variety of instrumental methods.
Serpentine occurs in a variety of wonderful translucent to nearly transparent green and yellowish green colors that look very much like jade. It is a metamorphic mineral that is often found in the same geographic areas and same types of rocks as jade. Serpentine is significantly softer than jade and also has a much lower specific gravity.
Vesuvianite, also known as idocrase, is another jade look-alike that is very difficult to distinguish from jade without laboratory testing. It has similar hardness, specific gravity, and physical appearance. It is not nearly as tough as jade and will break easier - but that requires destruction of the specimen.
Maw Sit Sit is a rock with a bright chrome-green color mined in Myanmar. It has a very similar appearance to jade. Maw sit sit is composed of jadeite, albite, and kosmochlor (a mineral related to jadeite). It is used to cut cabochons, beads, and make small sculptures, and is easily confused with jade.
Hydrogrossular Garnet is a green massive variety of garnet that is usually green in color with black markings. It looks so much like jade that in South Africa, where it is common, it is known as "Transvaal Jade." It is frequently cut into beads, cabochons, and small sculptures.
Aventurine is a trade name used for a green quartz that is often colored by fuchsite inclusions. These typically color the quartz a light to dark green color and produce some aventurescent sparkle. Aventurine is sometimes confused with jade.
All of the above natural minerals and rocks can be confused with jade. Many people like them, enjoy them, and knowingly purchase them for that reason. It is important to know that these jade look-alikes, along with plastic and glass made into objects in the same style as jade, are abundant in the market place. Know what you are buying or purchase from a dealer you can trust if you are shopping for these items and desire jade instead of an alternative. Errors and deception are common.
Geography of Jade
Most people immediately think of China as the source of jade and jade objects. China has always been an important producer of jade, a leading jade cutting center, jade consumer, and jade market. The only time dominance in any of these activities moved outside of China was between World War II and the early 1980s. At that time the Chinese government suppressed jade commerce, and Hong Kong temporarily became the center of jade commerce.
Jade jewelry and jade artwork are extremely important in China. Jade is more important in China than the importance of diamonds in the United States. Per-carat prices for the best imperial jade in China rival the per-carat price paid for diamonds in the United States.
Since prehistoric times, jade has been used to make tools, weapons, and important ornamental objects in Asia, Europe, Australia, the Americas, and numerous Pacific islands. The toughness of jade made it an excellent material for making tools and weapons.
Because of its beauty, people held jade in highest esteem and used it to make religious art and ornaments for their rulers. None of these ancient cultures had contact with one another, yet they all independently used jade for many of their most sacred and important objects. Such is the appeal of jade.
Geologic Occurrence and Jade Prospecting
Jadeite and nephrite are minerals that form through metamorphism. They are mostly found in metamorphic rocks associated with subduction zones. This places most jadeite and nephrite deposits along the margins of current or geologically ancient convergent plate boundaries involving oceanic lithosphere.
Jadeite is typically found in rocks that have a higher pressure origin than nephrite. This normally causes a geographic separation of jadeite and nephrite deposits.
From ancient times, much of the prospecting for jade has been done in the steeper parts of drainage basins, where pebble- to boulder-size pieces of rocks are found in stream valleys. Boulders and pebbles of jade normally have a brown weathering rind that hides their inner beauty and potential value.
Prospectors search these valleys looking for jade boulders. Small windows are often cut into the boulders in the field to assess the material's quality and to determine if it is worth the labor of transport.
Jade boulders can be very difficult to transport without damage. Human and animal labor was the only way to transport them historically. Today in some areas that is still the only way to move the boulders to market. Where economics allow, a helicopter with a basket or sling on a cable will fly in to difficult areas. Workers on the ground will load jade boulders, and the helicopter will lift them out. Although helicopters are very expensive to use for this type of work, one nice boulder can be worth many thousands of dollars or more in rough form.
Some jade is also mined from hard rock deposits. Boulders are sometimes mined from ancient conglomerates, but ophiolite exposures are the most important type of hard rock deposit. Ophiolites are the metamorphosed rocks of ancient subduction zones, now exposed at the surface by faulting or uplift, followed by exhumation by weathering. Jade is mined from ophiolites by both surface and underground methods.
Geographically, much of the world's jade is found around the rim of the Pacific Ocean, where subduction transports large slabs of oceanic lithosphere beneath continents and volcanic island arcs. This accounts for much of the jade found in South America, Central America, the United States, Canada, eastern Asia, and New Zealand.
Perhaps the most attractive and valuable jade found in the United States is from the area around Jeffrey City and Crooks Gap in Wyoming. There, nephrite jade is found by prospecting alluvial sediments, looking for jade in stream-rounded pebble- to boulder-size pieces.
Social Importance of Jade
In the United States and Europe, diamonds, rubies, sapphires, emeralds, opals, garnets, and a few other gems are much more popular than jade. Jade is not thought to be as precious in these regions as it is in China.
The Chinese have a much higher regard for jade than any other people. For thousands of years, jade has been the most popular gemstone in China. Chinese emperors desired excellent specimens of jade, and they traded or waged war with distant people to acquire them.
In China, gifts made from jade are given at almost every important station in life, such as birthdays, anniversaries, marriages, and other celebrations. It is also a commonly used material for producing religious art. China is the country where the importance of jade is the highest.
Contributor: Hobart King
|Geology of Gems|
|Ruby and Sapphire|
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