Sunday, March 3, 2013

Jade - An Extraordinary Gemstone

 This sample of jade shows the extreme deformation required to produce jade. Numerous fractures in the original rock
 allowed fluids to fill open spaces and replace the original basalt with dark green nephrite jade, while fractures were
 rehealed with white jade and finally, after things started to calm down, later fractures were filled with apple green jade
 veins before Mother Nature uplifted the Granite Mountains in Wyoming allowing erosion to free the jade over millions
 of years. Specimen from the Jay G. Sundberg collection.
Extraordinary pressures, temperatures and chemistry are required to produce jade. The metamorphic fluids released by minerals in rocks at great depth within the earth's crust are so caustic that they replace original minerals and rocks. Over the years I found pseudomorphs of jade after quartz and even jade replacing the matrix and feldspar in trachyte porphyry!

Emerald green jade with quartz inclusions 
(Jay G. Sundberg collection).
As metamorphogenic fluids migrate into adjacent rocks, they alter and replace rock-forming crystals at great depth in the earth's crust. They even leave a aureole of alteration assemblages that can be used by a trained geologist and prospector to find hidden jade deposits. Such altered zones may be partially exposed at the earth's surface following millions (even billions in some cases) of years of deformation, uplift, and erosion. When prospecting in the Granite Mountains for gold and ruby, many alteration haloes were identified suggesting that either a jade deposit was hidden at shallow depth, or the jade had already been removed by Mother Nature's erosion and scattered into the adjacent boulder conglomerates along the flanks of the Granite Mountains, and in particular, near Jeffrey City and Crooks gap. Some years ago, I even had a rock hound bring me samples of ruby schist that look very similar to the Red Dwarf ruby deposit near the Graham Ranch. But instead of being in place like those deposits at the Red Dwarf, these cobbles were found on Green Mountain. The cobbles and boulders from the Green Mountain-Crooks Gap-Jeffrey City area represent the erosional remnants of a major mountain range denudated by erosion over millions of years. The late Dr. J.D. Love of the US Geological Survey described this former range as being as high as the alps, in his excellent USGS professional paper on the Granite Mountains

Prismatic white quartz crystal preserved in dark green jade (Jay G. Sundberg collection).

Another sample of prismatic quartz preserved in jade. The original rock was likely a high magnesium basalt. The entire
 rock matrix of the former basalt was replaced by the nephrite jade while leaving the quartz crystal untouched (Jay G.
 Sundberg collection).
Hexagonal jade? This is a piece of prismatic quartz which was entirely
replaced by nephrite jade. Note the specimen exhibits a distinct hexagonal
crystal habit typical of quartz (but not of jade). Specimen found in the 
Tin Cup district of the Granite Mountains (W. Dan Hausel collection).

Jade cabochon with feldspar (Jay G. Sundberg collection).
Pitted jade (Jay G. Sundberg collection).
Mirror of Jade with jade plant. This specimen from the Jay Sundberg collection has such a high polished reflective surface
 that it can be used to comb your hair.

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hundreds of gemstones, gold anomalies, previously unreported minerals
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Do you have a specimen that might be jade? This book provides 
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Arrow head carved from Wyoming jade (Jay Sundberg collection).

Spearpoint carved from nephrite jade.

Now you can see why all of the jade found in Wyoming is known as Wyoming Jade (nephrite).

Thursday, October 29, 2009

Jade - how to find this extraordinary gemstone.

Jade is the gemologist's term for two different mineral species: nephrite and jadeite. These two minerals are nearly impossible to distinguish from one another without the aid of mineralogical and XRD (x-ray diffraction) tests.

Nephrite is categorized as an amphibole and consists of extremely dense and compact fibrous tremolite-actinolite; and jadeite is categorized as a pyroxene, and also forms dense and
compact material.

This map from the Wyoming Geological Survey is unfortunately misleading. The only place in the state where neprhite
 Jade has been identified is in the central part of the state in the Granite Mountains and Crooks-Gap Green Mountain near 
Jeffrey City. All other localities are questionable. For example, the author was unable to find any jade in the Seminoe Mountains
during two years of field investigations (Hausel, 1993, 1994), and the occurrence along the southern edge of 
the Wind River Mountains (Prospect Mountains) was later examined and all the material reported as nephrite jade was
 amphibolite (Hausel, personal field notes).
Many rocks are mistaken for jade. Some of the more common include rounded, stream-worn or wind-polished cobbles of amphibolite (a dark metamorphic rock that resembles dense basalt), metadiabase (another dark metamorphic rock that also resembles basalt), epidotite (a dense pistachio green rock), quartzite (granular rock that can be white, dark gray, green or other colors) and serpentinite (dark green rock that can be scratched with a pocket knife). These rocks can be distinguished from jade by a couple of tests including simple field observations. For example, amphibolite and metadiabase have granular texture that is lacking in most jade (jade is smooth and massive without granular texture). A freshly broken surface of quartzite will sparkle in sunlight due to the reflection of light bouncing off individual quartz grains; and epidotite has a distinct pistachio green color (unlike jade). One of the more common rocks and minerals mistaken for jade is serpentinite (a rock formed mostly of serpentine). Jade is tough and hard, whereas serpentinite is relatively soft and can be scratched with a pocket knife. In addition, serpentinite will have pockets or zones of weak to moderate magnetism that can be detected by a geologist’s magnet. I’ve never seen a piece of magnetic jade, although some probably occurs.

I’ve seen serpentine sold to unsuspecting tourists as apple green jade. I even showed one rock shop owner from Riverton that all of the material he was selling as high-quality jade was serpentinite, but he refused to listen and continued to sell it as high-quality apple-green jade – and probably still does to this day.

When prospecting for jade, note that large jade boulders will ring when struck by a hammer. They feel much heavier than ordinary rocks, and are much smoother and denser than other boulders. Some boulders and cobbles of jade are so smooth that it gives an impression the stone was polished in a rock tumbler. Jade feels slightly sticky when wet and prospectors will look for a “show point,” area where the green color shows through altered rinds that encrust much detrital jade.

Light green muttonfat jade from the Granite Mountains. Note the crystal is
hexagonal (6-sided) just like quartz. This jade replaced a former
quartz crystal leaving behind this rare pseudomorph) (W. Dan Hausel,
Jade never shows external crystal structure except in rare cases where it pseudomorphs, or mimics the crystal habit of another mineral. I had heard about this phenomenon from a couple of rock hounds over the years, but never witnessed it until about 15 years ago when I found a pocket of hexagonal jade in the Granite Mountains (Wyoming) northeast of the Red Dwarf ruby deposit near the Tin Cup area that had the same crystal habit as quartz.

Microscopically, jade will form a mass of matted, intricately interwoven fibers that produce an extremely tough gemstone resistant to fracturing. Mineral toughness is rarely considered in mineralogy books, but any discussion of jade always leads to a discussion of toughness. The toughness of a mineral is represented by its fracture strength or ability to resist fracturing, which is about 30,000 psi for nephrite. In other words, it takes a lot of pressure to fracture a coherent piece of jade. Only carbonado, a black granular to compact industrial form of diamond, is tougher than jade; whereas gem-quality diamond is hard, but not all that tough. Gem diamond can scratch almost anything, but it can be smashed with a little effort with a blow from a hammer. It is the toughness of jade, combined with hardness that makes the gem carvable, durable and unique.
Look closely at this jade and you will see several individal jade crystals that are roughly hexagonal. These are also jade
 pseudomorphs after quartz. During the geological past, the jade slowly replaced the quartz one atom at a time without
 disturbing the original crystal habit of the quartz (W. Dan Hausel, collection).

Jade ranges from opaque to translucent masses and has a vitreous to waxy luster and is reported in a variety of colors including black, white, and several shades of green. The green color is due to the presence of iron. When iron is absent, the mineral is practically colorless to cloudy white, resulting in a variety known as ‘muttonfat jade’. Other varieties of jade include translucent, emerald-green ‘imperial jade’; ‘apple-green’ jade, ‘olive-green’ jade, ‘leaf-green‘ jade, ‘black‘ jade, and ‘snowflake’ (mottled) jade. The greater commercial values are attached to the lighter green translucent varieties. Rare emerald green jade is colored by iron and trace amounts of chromium.

The extraordinary color of apple
 green jade from Wyoming.
The origin of nephrite jade was investigated in the 1960s. It is thought that nephrite formed by metasomatic alteration of amphibole during metamorphism. This means that hot fluids reacted with existing amphiboles and slowly replaced them by extracting some atoms and replacing those atoms with new atoms. In Wyoming, this happened when these rocks were buried under several miles of rock about 2 to 3 billion years ago. Blocks of amphibolite were disrupted and trapped in a molten granitic rock and portions of the amphibolite (xenoliths) were altered to jade by the hot granitic fluids. These reactive fluids not only produced jade, but they also altered the surrounding rocks to produce a group of minerals that included clinozoisite, zoisite, sericite and chlorite.

When found in outcrop, nephrite jade is associated with this distinct assemblage of minerals that form an alteration halo around jade. This halo consists of bleached leucocratic (white) granite-gneiss that is mottled pink and white, some secondary greenish clinozoisite, pink zoisite, pistachio green epidote, green chlorite and fine white mica. This alteration halo can be used as a guide to find hidden jade deposits. While exploring between some jade deposits north of Jeffrey City to the jasper deposits in the Tin Cup district to the west, I found more than a dozen such halos – a couple had exposed jade, others did not. The ones without jade, such as shown in the photo below, likely have hidden jade at shallow depth.

Wallrock alteration found with jade includes bleached white granite
gneiss with pink zoisite, green chlorite and trace epidote. While
searching north of Jeffrey City, I found more than a dozen areas
with this characteristic alteration halo. Where found, this halo represents
places where jade or hidden jade is likely to be found (with some digging). 
The name jade comes from the time of the Spanish conquest of Central and South America where jade and jade carvings were prized as much as gold by the Aztecs. The Spanish used the name piedra de hijada, or stone of the side, because it was believed that jade cured kidney ailments when applied to the side of the body. The Spanish also called this stone kidney stone or piedros de los rinones, which translated into Latin as lapis nephriticus. The term nephrite anglicized the Latin term for jade. Nephrite has been known as ‘axe-stone’ because many nephrite stone artifacts have been found that were shaped into axe-heads due to its toughness. Although primary deposits of jade are important, much of the finest material comes from secondary alluvial deposits.

Some incredible pieces of jade have found their way to the jewelry industry. For example, one small jadeite ring sold for more than US$2.4 million: a 27-bead emerald green jadeite necklace 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!

Black Jade from Wyoming
All of the jade found in Wyoming is nephrite, whereas much of the jade mined in the Orient is jadeite.

Translucent Jade cab 
from Wyoming

For those interested in searching for jade in Wyoming, it is found primarily in the Granite Mountains and to the south at Crooks Gap-Green Mountain. It has been reported elsewhere in the state, but much of the material reported outside of the Granite Mountains has turned out to be serpentinite.

The best jade specimens found in Wyoming are peb­bles and boulders in alluvial fans and soil around Jeffrey City. Cobbles and boulders are found south of US Highway 287 (789) while jade (in place) is found in outcrops to the north of the highway in the Granite Mountains.

Another strange rock. A former igneous rock (trachyte porphyry) from
the Granite Mountains, Wyoming, that was replaced by nephrite jade (W.
Dan Hausel collection).
The jade localities are described in the following books:

Hausel, W.D., and Sutherland, W.M., 2000, Gemstones & Other Unique Minerals & Rocks of Wyoming - A Field Guide for Collectors: Wyoming Geological Survey Bulletin 71, 268 p.

Geisha dressed in jade - 
colored pencil sketch.
Hausel, W.D., 2006, Minerals & Rocks of Wyoming, A Guide for Collectors, Prospectors and Rock Hounds, WSGS Bulletin 72, 125 p.

Hausel, W.D., and Sutherland, W.M., 2006, World Gemstones: Geology, Mineralogy, Gemology & Exploration: WSGS Mineral Report MR06-1, 363 p.

Hausel, W.D., 2009, Gems, Minerals and Rocks of Wyoming. A Guide for Rock Hounds, Prospectors & Collectors. Booksurge, 175 p.

A great majority of in situ jade is found north of Jeffrey City (T30N, R92-93W). Many were prospected in the past and thus most are now marked by old prospect pits. Look on Google Earth for prospect pits and then visit them.

Massive emerald green Wyoming jade
Jade was at one time highly sought after by Wyoming prospectors. But much of the high-quality easily found, emerald-green and translucent jade was found in Tertiary conglomerates at Crooks Gap. Lower quality light-green jade was found in place to the north of Crooks Gap in the Granite Mountains, but the source of the valuable emerald green was never identified and remains to be found. In the 1930s and 1940s, many jade boulders weighing several hundred pounds were found near Jeffry City in central Wyoming.

Jade carvings
Jadeite has never been found in Wyoming. It forms at high-pressure and low-temperature from near surface to depths as great as 30 miles. Geologically, it is found near convergent continental margins (where there is considerable pressures and temperatures from tectonic stress), and forms by fluid interaction with serpentinizing peridotite at depth. It occurs in veins and masses within metamorphic rocks, particularly albitite, actinolite schist and/or serpentinite. Most jadeite is found in highly faulted, subduction-related serpentinite or m̩lange along major fault zones Рsuch as in California.

Extraordinary specimen of polished
 jade from Wyoming with rind
Only three countries produce jadeite on a commercial scale: Burma, Guatemala and Russia. The jadeite from Guatemala is granular, mottled, and opaque. Burmese jadeite has more intensely saturated colors of deep-lavender to emerald- imperial green. Jadeite from Russia, although generally dark-colored, tends to sit between the Burmese and Guatemalan jadeite. Jadeite has not been identified in Wyoming.

Nephrite jade is produced primarily by Canada. Wyoming produced large quantities of fine nephrite in the past, but there is no longer commercial production. Russian nephrite was exported to China in the past and most Russian jadeite was sold through markets in Hong Kong as Burmese jadeite. In Eastern Turkistan, the jade market is strictly controlled by the Chinese government and only government buyers can purchase jade at the price set by the government.

Can you guess which of the two minerals above is jade? The specimen to the right (above) is weakly magnetic, with little zones of magnetism best  detected with  a pencil magnet (see And with a little effort, it can also be scratched with a pocketknife, unlike the real jade (nephrite) to the left.

Intrigued by all of the treasures out there in the world to be found? There are geological hints on where and how to find jade and hundreds of other mineral deposits. Many of these are described in my books  at Amazon.

W. Dan Hausel, a.k.a the GemHunter, was privileged to work as a research geologist for the Wyoming Geological Survey at the University of Wyoming for three decades. During those years, he periodically took leave of absence to consult on gold, diamond, and gemstones in the search for additional deposits outside of Wyoming. Over the years, he published more than a thousand books, maps, professional papers and abstracts, and mapped more than 1,000 square kilometers of complex geological terrain, while finding hundreds of mineral anomalies including one of the largest gold deposits ever found on earth (with 6 colleagues).

Wow, can you believe this specimen? Jaded brains. That's right, the last State Geologist I worked for at the Wyoming Geological Survey had his brains removed and we examined them under a microscope and found them to be replaced by jade (just kidding - about the replacement - there were no brains to be found).

My good friend, Dr. J. Dave Love (RIP) sits on large Wyoming jade boulders in a garage in Wyoming.