Introduction: Nephrite is one of the minerals commonly called jade, the others are jadeite and omphacite. Mineralogically, nephrite is a fibrous variety of the actinolite-tremolite series. The cabochon above is from Lake Baikal in Russia and weighs 4.95 ct.
Colors: translucent to opaque; light to dark green, also yellow, brown, white, gray, black, sometimes mottled. Nephrite, with few exceptions, is usually in dark shades and never attains the fine green of Imperial jade (jadeite).
Stone Sizes: Alluvial boulders of several tons are not uncommon in certain localities. Large, fine pieces are usually carved. It is also commonly cut as cabochons or beads. The Smithsonian displays a large boulder alongside a thin slab, backlit to show the color.
-Taiwan (Fengtien): found in seams in the host rock, spinach green in color.
-Australia and New Zealand: in boulders, usually dark green to black
-China (Sinkiang Province): generally lighter in color
-Russia (Lake Baikal): distinctive and fine color; dark spinach green color with abundant black inclusions of graphite
-Poland (near Jordansmuhl): creamy white to gray-green with green patches
-Alaska: green colors in large masses, sometimes fibrous
-California: various green shades in alluvial boulders, sometimes as large as 1000 pounds.
-Wyoming: distinctive boulders mottles green and white
-Usually none (N) but on rare occasions, it has been dyed to alter color
-Refractive Index: 1.606-1.632 (+0.009, -0.006), usually spot reading of 1.61
-Birefringence: usually not detectable
-Optic Character: AGG
-Specific Gravity: 2.95 (+0.15, -0.05)
-Hardness: 6 to 6.5
-Chemical Composition: Ca2(Mg,Fe)5Si8O22(OH)2
-Cause of Color: generally iron
-Absorption Spectra: rarely shows a diagnostic pattern; sometimes a vague line at 500 nm as well as lines in the red in green stones of exceptional quality.
-Cleavage: not visible due to aggregate structure
-Phenomena: Chatoyancy (occasionally)
Name: Nephrite is from the Greek word, nephros, meaning kidney due to the shape of the rounded, organ like shape of nephrite boulders and pebbles.
Dates: Nephrite is the gem for the 12th anniversary.
Care: Nephrite can be safely cleaned in the ultrasonic, steam cleaner as well as warm, soapy water.
To see available nephrites, click here.