Turquoise

Turquoise
By Bill Gallagher
720 Words
ok to reproduce not for profit in entirety w/credit



Turquoise occurs as many different types, and thats because each locale from which this stone derives imparts a discernible and unique personality to the stone.  The host rock of turquoise has a lot to do with specific characteristics of hardness and color, though turquoise forms in the same basic way, as a Hydrated Phosphate of Copper and Aluminum, in the same basic colors of blue and green, where ever it is found, and that is because of copper somewhere in the nearby vicinity.  It is the degraded forms of copper which actually give turquoise its color.  As an aside, though related, it is thought that a lot of this same degraded copper material may have also been directly responsible for the rediscovery of smelting, because the powders of malachite, azurite, chrysocolla, and even turquoise were probably used to color early pottery.  After the firing of the pottery there were surely metal droplets within the bottom of the furnaces, and this led to the Chalcolithic Period, which quickly became the Bronze Age.

Blue is by far the most common color of Turquoise, ranging from a very pale, almost whitish blue, to a dark sky blue, and this can also be witnessed by the fact that the very word Turquoise is synonymous with the color blue, even among people far removed from the basic understandings of this rock formation.  Green turquoise occurs occasionally and goes through periods of being acceptable, or hot, or not.  Right now we seem to be coming off a period where green turq was all the rage, and heading back towards deep dark blues as those types most in demand. The word Turquoise is probably rooted in the word Turk, denoting the Levantine traders who initially dealt in this rarity to Europeans.  The finest grade of Turquoise to this day is known as Persian grade, another reference to the earliest known deposits which were probably in and around modern day Iran. Some white turquoise has been found, which would be Hydrated Phosphate of Aluminum, without the copper content.  Although white turq is rare,  it is really beyond the scope of most turquoise cutters, who do not really care about a soft white rock when things like meerschaum and howlite are readily available and very inexpensive.

Overall turquoise as a formation is fairly rare.  It is considered to be a product of meteoric origin, which means rain.  Rainwater washing down through host rock caused further degradation, and secondary deposition which became turquoise.  I know.  It sounds funny, but there you have it.  No one was around to watch, so its really still a lot of guesswork, although turquoise definitely seems to be something of an anomaly, just looking at it, and the way it forms in both nodules and thin veins together.  Turquoise is crystalline in form, though visible crystals are extremely rare and high dollar as specimens.  The stone ranges downward in hardness from 5-6 to what is called chalk.  Chalk and hard chalk are very soft and the label tells the story here.  Most turquoise today is treated in some way, whether it be to harden it, deepen the color, or both.  Good hard natural turquoise commands a premium and is hard to get most of the time.

Some of the finer American Turquoise comes from Arizona and even New Mexico.  Morenci can be killer stuff, Kingman, Bisbee, Sleeping Beauty, Santa Rita(RARE)....they all have their high and low grades of course, and there are literally hundreds of Turquoise mines throughout the western United States.  I have seen some fine Morenci turquoise go for as little as $50.00 a pound, though the Bisbee, Sleeping Beauty, and Kingman are quite a lot more pricey than that, running into the hundreds of dollars per pound and up.   Some Arizona and New Mexican turquoise is mined from degraded feldspar deposits called Caliche (Cuh-lee-chee), a soft, corroded magmatic crystalline stucture, like orthoclase.  Some of this host matrix still possesses identifiable crystalline form.  The amount of silica or feldspar in these host matrices dictate the hardness of the Turquoise within, along with other traits which give each locale its signature types.  Also included in traits and types are the various inclusions which most turquoise will exhibit, such as the dark brown matrix common throughout the Hachita turquoise.  Lander county Nevada, home of the Royston type of Turquoise, The Northern Lights, Carico Lake and many others, is all very hard turquoise and many times mined from hard rock with jack hammers.  The material from Lander County usually starts around $500.00 per pound, and just gets higher and higher as the quality, size, and color improve.







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       Most of the turquoise used by the Tiffany Company in the late 19th century and late 20th century came from a mine located between Cerrillos, New Mexico and Santa Fe, New Mexico.   I toured the mine about 20 or 25 years ago and have a few small nuggets of gem quality turquoise from there in my collection.  At that point the mine had been worked off and on for a few hundred years with clear evidence of mining by Native Americans prior to the arrival of the Spanish.   Much pretty than most of the pieces I've picked up in other locales since (but that's mostly my personal opinion)

BA

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Whatever the source, quality turquoise is a thing of beauty....Finding quality material even in known areas of production can be a real challenge though, which is part of the reason so much of the older (especially cheaper) jewelry was made with either reconstituted or otherwise treated jewelry.   Back in the old days when my grandpa lived on the Navajo reservation soaking lower quality stones in either vegetable oil or paraffin was a common trick of the unscrupulous.

BA

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Great article Bill,lots of interesting information,guess this has been a life long hobby ?

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