Nephrite colors do not match in cither variety or intensity the colors of jadeite. With few exceptions, nephrite shades are usually dark and somber, and nephrite never attains the fine green of Imperial jade (jadeite). The Chinese long ago mastered the art of carving nephrite, and immense brush pots and statues grace many museums around the world. Of special note is the M. M. Vetleson jade collection that occupies an entire room at Smithsonian Institution (Washington, D.C).
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Is a Variety of||Jade|
|Crystallography||Monoclinic. Masses of fibrous crystals, densely packed and very tough.|
|Colors||Creamy beige (mutton fat jade) when rich in Mg. Green colors, due to Fe. Brown (oxidized Fe); sometimes a surface skin is dark brown. Also yellowish, grayish brown, yellow-green, black.|
|Luster||Vitreous to greasy; dull.|
|Density||2.90-3.02; usually 2.95.|
|Cleavage||None. Fracture splintery. Very tough.|
|Stone Sizes||Alluvial boulders of several tons are not uncommon in certain localities. Large fine pieces are always carved, for example, the sculpture Thunder, by Donald Hord, in Wyoming jade (145 pounds). American Museum of Natural History (New York): displays a huge block of nephrite from Poland weighing 4718 pounds. Smithsonian Institution (Washington, D.C): displays a boulder of several hundred pounds, sliced open, with a thin slab backlit to show the color.|
|Spectral||Doublet at 6890, two vague bands at 4980 and 4600; sharp line at 5090.|
|Pleochroism||Strong dichroism, masked due to the fibrous nature of the material.|
Fibrous variety of Actinolite.
Optics: a =1.600-1.627; γ= 1.614-1.641.
Biaxial (-). Usually refractometer shows a shadow edge at about 1.62.
Occurrence: Nephrite is most frequently encountered in the form of rolled boulders.
Wisconsin: gray—green color, not too attractive.
Alaska: green colors, in very large masses, sometimes fibrous (chatoyant).
California: alluvial material, various green shades, in boulders up to 1000 pounds.
Lander, Wyoming: boulders mottled green with white —very distinctive material.
New Zealand: Maori Greenstone, in situ and in boulders, usually dark green to black.
Fraser River, British Columbia, Canada: dark-colored nephrite, little of which is very fine quality.
USSR (at Lake Baikal): dark spinach-green color with abundant graphitic black inclusions or spots—very distinctive jade, fine color.
China (Sinkiang Province): generally light in color.
Poland: creamy white to gray-green, with green patches (near Jordansmuhl).
Fengtien, Taiwan: spinach green to pea green, in seams in rock; despite abundance of material on market in former years, large pieces are very scarce. Also catseyes noted.
Cowell, South Australia: material similar to New Zealand; large amounts potentially available. _
Mashaba district, Zimbabwe; Germany; Mexico.
Comments: Nephrite colors do not match in cither variety or intensity the colors of jadeite. With few exceptions, nephrite shades are usually dark and somber, and nephrite never attains the fine green of Imperial jade (jadeite). The Chinese long ago mastered the art of carving nephrite, and immense brush pots and statues grace many museums around the world. Of special note is the M. M. Vetleson jade collection that occupies an entire room at Smithsonian Institution (Washington, D.C). Carvings have been done using only one side of a jade boulder, leaving the rough shape as a background. Fine use is also made of the weathering skin (brownish) of green nephrite, creating a cameo effect, sometimes displaying great detail and fine workmanship.
Catseye nephrite from Taiwan has also been reported. The catseyes are due to parallel arrangement of fibers (ferroactinolite content = 10%). The colors found include greenish to honey yellow, dark green, dark brown and black. The properties are as follows: a = 1.613-1.616; β=1.626; γ=1.632—1.637; birefringence = 0.016; S.G. = 3.01-3.05.
Name: From the Greek word nephros, meaning kidney; the rounded, organ like shape of nephrite boulders and pebbles undoubtedly stimulated people to regard these stones as magical cures for the organs they resembled, through sympathetic magic. See also: Jadeite.