Jade is a name which is given to two different metamorphic stones, Nephrite and Jadeite. Each of these stones are composed of different silicate minerals. Nephrite jade is the original stone of heaven which has been revered by the Chinese for thousands of years.
Nephrite is a variety of a calcium and magnesium-rich amphibole mineral actinolite (which also makes up a certain form of asbestos). The chemical formula of nephrite jade is Ca2(Mg,Fe)5Si8O22(OH)2. Its crystal habitat is massive and it is of the monoclinic crystal system.
Nephrite jade takes on a high polish which is vitreous to greasy. Its fracture is splintery to granular. Nephrite has a refractive index is 1.606 to 1.632.
The Hardness and Toughness Of Nephrite
Nephrite is more common than its harder counterpart, jadeite. Though it is softer (measuring a 6 to 6.5 on the Mohs scale, compared to the 6.5-7 of jadeite) it is actually a much tougher stone. Hardness is an attribute measured by how easily it can be scratched. A diamond measures the hardest on this scale at a 10, it can scratch anything while it cant be scratched by anything other than another diamond. Both nephrite and jadeite are harder than steel, if you can scratch a stone with a knife it is not jade.
Toughness measures the brittleness or the ability of a material (or in this case a mineral) to break. According to the Ministry of Energy, Mines and Petroleum Resources of British Columbia the fracture strength of nephrite is about 200 MN/m2 whereas that of jadeite is about 100 MN/m2 which is an impressive quality of nephrite. It is commonly known as the toughest natural mineral on earth.
Types of Nephrite and Their Colors
The color of nephrite can vary depending on its source and quality. Commonly it is envisioned as an imperial green stone yet can hold almost any shade of green, blue, red, orange, black, white, violet, orange, brown and yellow.
Various colors of nephrite jade are unique to their individual sources such as the rust colored vulcan Big Sur jade which can be various colors of brown, red, yellow and orange.
Certain shades of green are also unique depending on the areas of the world it is found, one example of which is the gem quality polar jade of British Columbia (you can read an amazing article about Polar Jade over at Timeless Jade).
As nephrite is found all over the world and in greater amounts than jadeite, it is less valuable and less expensive except for the finest of specimens. Some high quality nephrite jade does appear in some locations such as in Big Sur, California and in parts of British Columbia. Some specimens of nephrite jade from these areas are among the finest quality specimens in the world.
One unique specimen of nephrite jade comes out of Big Sur and is known as botryoidal jade. This type of jade is commonly known as bubble jade and is formed in nodes within serpentine.
History Of Nephrite
Throughout history nephrite jade has been utilized in a wide variety of ways. Some of these include as funeral ornaments, weapons, jewelry and as a ward against kidney ailments. It has been utilized for thousands of years by various cultures.
One ancient legend from China states that in the beginning of time man was put on earth and was plagued by all of the wild animals of the world. The gods sympathized with man and cast jade axes from the heavens onto the earth for them to find. This stone was henceforth called the stone of heaven.
Another legend surrounding nephrite comes from China. According to the tale a man named Bian He found a stone which he believed to be of high quality nephrite jade. He approached King Li of Chu with his find, who was unbelieving that the stone was actually jade and had one of Bian He’s legs cut off for playing him false. Once King Li passed Bian once again approached the ruler of Chu, King Wu, with his find. King Wu also believed that Bian He was playing him false and had his other leg cut off.
Bian He was not deterred. King Wu soon passed on and the new ruler King Wen was approached by Bian He, who god only knows his reluctance to show off his find. King Wen, actually believing that the stone was true jade, immediately sent off the find to his royal sculptors. To the sculptors amazement the stone was of the highest quality white nephrite which rivaled the value of all other pieces of jade and was the envy of many. The piece was soon called the He Shi Bi or The Jade Disk of He.
There are many legends revolving around this historical piece of jade. More can be found on our Chinese jade page. To paraphrase the rest of the legend the piece soon became the Imperial Seal of China and unfortunately due to a long history of wars and battles surrounding this singular piece of jade it has been lost to history.
Another specimen of nephrite jade rivals all others, this is known as the Nephripod which was discovered by Donn Wobber off the coast of Big Sur. His memoir Jade Beneath the Sea: A Diving Adventure tells of his discovery and excavation of a 9,000 pound bolder of nephrite in the 1970′s, which is now located in the Oakland Museum.
Value of Nephrite Jade
The value of nephrite can be relatively modest depending on its quality. Some attributes that can affect its price are its color, translucency, natural patterns, the location from where it originates and sometimes by the artist which carves it. High quality nephrite can be relatively expensive though should only be purchased through trusted dealers.
Though nephrite is a fairly common stone there are many fakes that are made out of various materials, as well as artificial colorings made by dyes and chemical treatments. Other stones are commonly mistaken for jade such as serpentine and soapstone. Care should be taken when purchasing jade to ensure that it is the actual stone.