The GemHunter

Professor Hausel's Guide to Finding Gemstones, Diamonds, GoldRocks & Minerals 

Jade - Green Gold

“Old Korean adage, Even jade has flaws."


Jade is a treasure with incredible value - just look at the small, simple, jadeite ring that sold for US$2.6 million, and the 27-bead emerald green jadeite necklace which sold in Hong Kong for US$9.3 million. In 1999, a 2-inch diameter (0.33-inch thick), jadeite bangle sold at a Christie's auction for US$2.6 million; and a jadeite cabochon of 1.4-inches in length sold for US$1.74 million. So, how much is jade worth per pound? Good question! It's worth whatever someone will pay for it. 

All jade in Wyoming is nephrite (an amphibole) similar to jade found in BC, Canada. Much jade in the orient is jadeite (a pyroxene). But, these two are indistinguishable by the naked eye and require x-ray diffraction to determine which is which. Jade has a hardness of 6 to 6.5, but it is extremely tough but carvable. A knife only has a hardness of 5.5, so one must find tools with a greater hardness to carve this mineral. Carborundum, corundum and diamond are harder. The specific gravity of jade is about 2.8 to 3.2 and it is often massive with relatively high heft and has a distinct slick surface. 

In central Wyoming, jade is found in Precambrian host rocks associated with a group of hydrothermal alteration minerals such as sericite, chlorite, epidote, zoiste and/or clinozoisite. When these are found together, it likely suggests that jade is nearby - at shallow depth, or possibly eroded away and sitting downslope in a nearby drainage. Some of the more valuable specimens of Wyoming jade were discovered in the 1950s in central Wyoming. However, the source of the high-quality jade was never found according to my good friend - the late Dr. David Love. Essentially all of the high-quality gem-grade jade in Wyoming occurred as detrital cobbles, boulders and pebbles in flats surrounding Jeffrey City and Crooks Gap in unconsolidated, Tertiary, boulder conglomerate and alluvium (some alluvial rubies were also found nearby). The only jade found in place lies in veins and replacement deposits north of Jeffrey City, in the old, Archean (>2.5 billion years old), basement rock. However, this jade is poor quality. So, somewhere, there is a hidden (or eroded) source for some of the best jade ever found in the world.

Nephrite jade never shows external structure, except when it (rarely) pseudomorphs a crystal habit of another mineral. In the Granite Mountains of central Wyoming near Jeffrey City, some nephrite is found pseudomorphing quartz. Such specimens form pseudohexagonal (six-sided prisms) of light-green jade. In other places, jade encloses quartz crystals.


Typically, nephrite forms irregular masses that lack cleavage. Microscopically, nephrite exhibits a mass of matted, intricately interwoven fibers actinolite-tremolite fibers. This form makes nephrite extremely tough and resistant to fracturing. Unless the rock has a schistose (foliated) fabric, rounded boulders of nephrite are essentially impossible to break with a hammer. Nephrite is a result of the alteration of pyroxene in metamorphic terrains. The nephrite form of actinolite-tremolite is one of the toughest minerals known - and it is NEVER magnetic, in spite of what some suggest!


Serpentinite can be a problem for jade prospectors as well as first time buyers of jade who are periodically scammed by sellers. Serpentinite is found in the jade fields of Wyoming and in British Columbia and many prospectors mistaken the rock for jade. I have seen rock collectors in Wyoming sell serpentinite as high-quality jade to unsuspecting buyers - even after I pointed out to the unscrupulous individuals that the material was serpentinite. Even though serpentinite will typically have a nice green color similar to jade, it is softer and can be scratched with a pocketknife. According to Hausel (2014, 2009, 2005) and Hausel and Sutherland (2000), serpentine, which is found in the Tin Cup district of the Granite Mountains, only has a hardness of 2.5 to 5.5 and has scattered pockets and disseminated magnetite, making the rock weakly magnetic. Jade does not have magnetite. In the past, one deposit known as the Game Warden's jade found in the southern Wind River Mountains, which caused quite a stir after it was discovered and reported to contain giant jade boulders, - likely was all serpentinite. When examined by the author several years ago, only serpentinized ultramafic komatiite, similar to that found at South Pass, could be found.


Greenish quartzite is sometimes mistaken for jade - but it has granular texture, and tends to sparkle in the sun, on a freshly broken surface. Epido­te is softer, like serpentine, and can also be scratched with a knife - it is also, distinctly pistachio green in the region of Wyoming's jade deposits. 


In Wyoming, nephrite occurs primarily in the Granite Mountains and has also been reported at scattered localities from the Wind River Mountains to the northern Laramie Range in a narrow, east-west band that encloses the Granite Mountains north of Jeffrey City. However, I was not able to verify occurrences in the Wind River Mountains. Individual Wyoming jade localities are described by Hausel (2014). Many are found within the Tin Cup district northwest of Jeffrey City (T30N, R92-93W), and marked by old prospect pits in the granite and gneiss.


Much of the high-quality, emerald-green and translucent jade, was found in Tertiary conglomerates at Crooks Gap in Wyomng.  In the 1930s and 1940s, many jade boulders of several hundred pounds were found near Jeffry City.


HOW TO IDENTIFY JADE

The following 'rules of thumb' are used in field identification of jade: (1) Nephrite is heavier than the average rock of the same size. (2) Nephrite cannot be scratched with an ordinary knife blade (if it scratches, it is likely serpentine or chlorite, or another similar appearing mineral). (3) Nephrite has smooth, almost waxy appearance. (4) If the end is ground off of a suspected jade speci­men, the fresh surface will not sparkle or glitter in the sun. (5) Nephrite is never magnetic. (6) Nephrite is associated with distinct alteration mineral assemblage of pink zoisite, white sericite, pistachio-green epidote, and dark-green chlorite. More information on the characteristics of jade and where it can still be found in Wyoming is published in a book on gemstones (Hausel, 2014).


REFERENCES CITED.

  1. Hausel, W.D., and Sutherland, W.M., 2006, World Gemstones: Geology, Mineralogy, Gemology & Exploration: WSGS Mineral Report MR06-1, 363 p.
  2. Hausel, W.D., 1986, Minerals & Rocks of Wyoming. Geological Survey of Wyoming Bulletin 66, 117 p.
  3. Hausel, W.D., and Sutherland, W.M., 2000, Gemstones and other unique minerals and rocks of Wyoming: Wyoming Geological Survey Bulletin 71, 268 p. 
  4. Hausel, W.D., 2009, Gems, Minerals and Rocks of Wyoming. A Guide for Rock Hounds, Prospectors & Collectors. Booksurge, 175 p.
  5. Hausel, W.D., 2014, A Guide to Finding Gemstones, Gold, Minerals & Rocks: GemHunter Books, 369 p.
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