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.
Some extraordinary pressures, temperatures and chemistry are required to produce jade. The metamorphic fluids released by rocks at great depth are so caustic that they replace the original rocks and even replace quartz. As the fluids migrate out into the rock they are replacing at great depth in the earth's crust, they leave a aureole of alteration assemblages that can be used by a trained geologist and prospector to find hidden jade deposits that may now be exposed at the earth's surface following millions (even billions in some cases) of years of deformation, uplift of mountain ranges 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 they jade had already been removed by Mother Nature's erosion.

Emerald green jade with quartz inclusions (Jay G. Sundberg collection).

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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