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 by geologist Dan Hausel, 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.

A guide that will lead you right to many gemstone deposits in Wyoming and
provide insights of what to look for in gemstone deposits. The author found
hundreds of gemstones, gold anomalies, previously unreported minerals
and even and some diamond deposits - no other geologist in the history of Wyoming found more.

Do you have a specimen that might be jade? This book provides 
the basics for rock and mineral
identification and is available at Amazon



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