Many people erroneously think that the turquoise is purely a product of the ancient Mesoamerican cultures that flourished before Columbus, but it's far older than that and far more dispersed throughout the globe.
Turquoise jewelry has been found interred with a 7,500 hundred-year-old Egyptian mummy. Turquoise beads from at least 5000 B.C. were traced back to Mesopotamia, the name for ancient Iraq. The Americas started mining it probably a millennium ago, and it has been uncovered in burial sites all the way from Argentina to the American Southwest.
Supposedly it was a white trader who first suggested to the Navajos that they might combine turquoise with silver. Whatever the origin of the practice, it has endured to this day. The turquoise was generally believed to shield individuals from snakebite, poison, eye disease, and falls. It was thought to impart power to its owner, and to invoke rain for the crops.
The turquoise was revered among the Native Americas. The Navajo claimed turquoise was a piece of sky fallen to earth, the Apache believed it aided warriors and hunters to aim more accurately, the Zuni thought it protected them from demons and the Aztecs reserved it for their gods, forbidding mere mortals to wear it. Even today, the polished beauty of a turquoise set in glowing silver evokes a mystical response from people.
Turquoise is an opaque mineral with a color range from blue to green to yellow-gray, while the stone's waxen luster only enhances its color. Turquoise was mined as far back as 6000 B.C., by the Egyptians in the Sinai, from where it was transferred through Turkey to Europe. In fact, some say that its name, Turquoise, comes from the French word meaning Turkish.
Turquoise has been mined in Northern Africa, Australia, Siberia, China and Europe, but by far the best turquoise comes from Iran and Tibet. Despite the quality of those stones, it is still difficult to discover really good, untreated turquoise. There have also been superlative deposits uncovered in the American Southwest. These stones have a pronounced white or brown matrix, as opposed to the black matrix found in the Mid-East, Asia and elsewhere around the globe.
The most famous turquoise jewelry in America comes from the Native American population, which as been working it for centuries. The Zunis in particular have created magnificent pieces of turquoise jewelry set in silver. Naturally, its popularity has led it to be mass-marketed, and in some cases imitated by fakes.
Although turquoise is mined around the world, the most famous turquoise jewelry comes from the southwestern United States. Without question, the Navajo and Zuni silversmiths from the Four Corners region of New Mexico and Arizona produce the finest. They create myriad forms of inlaid turquoise and silver jewelry, including rings, bracelets, necklaces, earrings, pendants, brooches, belt buckles, bola ties, watchbands, and even barrettes.
Nor will you have trouble recognizing the style. It's as distinctive as it is beautiful. Turquoise and shells are meticulously cut, fitted and inlaid contiguously in handcrafted silver jewelry, then sanded and polished to perfection. Some of the more contemporary versions include channel setting. The best of Native American turquoise silver jewelry still stands as a cultural expression of a proud people with a remarkable heritage, shown through the magnificence of their craftsmanship and imagination.
In addition to shell, the contemporary stylists of turquoise jewelry have also spun off tradition by combining a variety of other inlays, including lapis lazuli, purple sugilite, malachite, jet and coral. They also employ different types of shell, such as mother-of-pearl, spiny oyster, pink shell, white shell, melon shell and red abalone.
The lovely opaque blue of turquoise is produced by traces of copper in the stone. Elements of iron will also create a pretty, pronounced green hue. Oxides contribute to the stone's famous gray, brown or black veining.
The History of Turquoise
Turquoise has captivated man's imagination for centuries. When it came to the attention of man is unknown. We have archeological as well as literary references that pre date the Christian era by five millenia. The four bracelets of Queen Zar, found on her mummified arm, date to the second ruler of the Egypt's First Dynasty, approximately 5500 B.C. Although not specifically mentioned in the Bible, scholars believe that the robe worn by the high priest Aaron was adorned with turquoise. Aristotle, Pliny and others refer to stones that must have been turquoise. After the fourth or fifth century A.D., many writings appeared discussing the stone. Explorers such as Marco Polo took time to write about it.
Turquoise was likely found and used by early man. Certainly the prehistoric peoples of the Western hemisphere knew of the turquoise as we have found pieces in burial and archeological sites throughout the two continents. The Anasazi and Hohokam mined turquoise throughout our Southwest. Absolute evidence exists that these prehistoric people mined turquoise at Cerillos and the Burro Mountains of New Mexico, Kingman and Morenci in Arizona and the Conejos areas of Colorado. Turquoise was a popular trade item as so much has been found in archeological sites many hundreds of miles away from its source. A prime example is the Cerillos, New Mexico, turquoise found with the Aztecs.
It seems clear that turquoise was always considered a stone of life and good fortune and it even had healing properties. Many people from around the world found uses for turquoise in numerous ways. To mention a few: EGYPT- the earliest known use of turquoise and the first mines on the Sinai are known to have occurred with this civilization. Queen Zar's jewelry in 5500 B.C. has been mentioned. It had mystical powers and was used in Egyptian art, figures and ornaments. PERSIA- the legendary home of the world's finest turquoise, the mines are at Nishapur. Turquoise became a major trade and barter item for the early Persians. Persian turquoise was found in ancient graves in Turkistan, and in the first to third century A.D., in graves throughout the Caucausus. Persian stones were much coveted in Afghanistan, and as far north as Siberia. It was used in art, medicine, as well as in jewelry in INDIA. TIBET- also has their own source of turquoise usually a green cast, very hard stone. It has a significant amount of spider webbing. Turquoise was a highly revered item to the Tibetans who ranked them in six grades, the most expensive valued well above gold. Every Tibetan wore or carried a piece of turquoise throughout life. Turquoise was used for currency in many areas of Tibet. MONGOLIA- their knowledge of turquoise likely came from Tibet and China. It became immensely popular. CHINA- The history of turquoise in China dates to the thirteenth century A.D. Although mining did exist, most stone came from trade with the Persians, Turks, Tibetans, and the Mongols. Much Chinese turquoise was used for carving and in other art and decorative ways. It never became a precious stone for the Chinese as was Jade for example. Turquoise was unknown until the 18th Century in JAPAN. Turquoise was not of great import in early and medieval EUROPE. However, as Asian conquests of, and incursions into, Europe occurred the European's familiarity with turquoise increased. It became more popular during and folowing the Renaissance. Turquoise, as mentioned earlier, was a very important item to the early inhabitants of both NORTH and SOUTH AMERICA. The stone was used in religion, art, trade, treaty negotiations as well as for jewelry. It was considered by some to be associated with life itself.
A brief note on its medical uses. These varied from land to land and age to age. It was thought ot prevent injury through accident, prevent blindness (by placing perfect stones over the eyes or ground into a salve) and, as a powder, it was ingested to cure stomach disorders, internal bleeding and stings from snakes and scorpions. It found its way into the mystic arts. Its color could forecast good or bad, predict the weather and influence dreams. It was good for nearly every ailment to include insanity. As a good luck tailsman it found usage in nearly every culture.
Origin and Occurence of Turquoise
Turquoise consists of the chemical elements copper, aluminum, phosphorus, hydrogen, and oxygen in the form of water. Thus it is described as a "hydrous basic aluminum phosphate of copper." It is also described as "hydrous aluminum phosphate colored by copper salts."
Its chemical formula is: (CuAl6 (PO4)8 4H2O)Note: with much variance.
This molecular structure permits the inclusion of other materials, principally Iron (Fe), Calcium (Ca), Magnesium (Mg), Manganese (Mn), Silicon (Si), and Zinc (Zn). These additional elements when incorporated in the molecular structure of turquoise influence its color and hardness. More on this later.
All of the above must come from the proper minerals being present in a finite area which must be geologically broken down from the areas rocks, dissolved, transported, and deposited in the proper concentrations in spaces, cracks, openings and hollows in subsurface rocks. It also must so remain in these "host" rocks for millions of years above the water table. One must understand that over these enormous periods of time mountains rise and wear away and seas form and disappear. In order to have a specific grouping of minerals remain collocated over such a period of time and then to have them undergo the proper pressures and temperatures to form turquoise is quite remarkable.
Turquoise deposits usually occur in areas with some volcanic or thermal history. Volcanic rocks such as phyolite and trachyte contain the larger percentage of turquoise formation. This is followed by intrusive rock formation with metamorphic and sedimentary rocks being the least likely to contain turquoise. That is not to say that turquoise has not been found in areas without igneous or volcanic activity. Turquoise has been found in the Sinai and in Australia. In these two areas it is found in sandstone and shale.
Most turquoise is found in "alteration zones," areas where the native, original rocks have been altered through the intrusion of other rocks from some volcanic or other thermal influence. The hydrothermal alteration is created by magmatic solutions from deep in the earth being forced to the surface through fractures or pores which eventually change the original rocks. This is due to the intense heat and chemical change thus associated between the new and the original rocks. All this, coupled with the long weathering of the surface rocks through wind and water and the resultant chemical breakdown of these rocks, creates the environment necessary for turquoise to form.
One other key geological activity is called silicification. It too is an act of hydrothermal and intrusive alteration. Here silica, which is a common associate of turquoise, is introduced into the turquoise deposit. This addition in periods of intense heat is responsible for the hardness of the turquoise and frequently the matrix as well.
The several steps and contingencies necessary to create turquoise are as follows. First there must be a source of copper. This occurs in a rather limited number of areas in the world. One must have a source of phosphorus collocated with the copper, usually from the mineral, apatite, which in turn is restricted to certain rocks not all of which are associated with copper. There must also be feldspar for the aluminum. There must be a deep hydrothermal alteration which breaks down the feldspars and frees the aluminum needed for the turquoise. The phosphorus usually comes from phosphoric acid leached from the apatite. The copper is usually introduced into the "host" rocks by the rising hot magma. The copper readily oxidizes near the surface and when in solution it reacts freely with the aluminum and phosphoric acid to form turquoise. At this time other minerals enter into the turquoise structure and create color variations.
Turquoise creation is affected by many other contingencies. For example; the best, hardest turquoise is found within 100 feet of the earth's surface (there are instances to the contrary - Lone Mountain for example.) Why? Well, as turquoise sits in its pocket waiting for someone to mine it, it is subject to the elements. If it's near the surface, it "drys out." It is less subject to the acids created by water percolating through the earth and is less likely to "soften" or become more porous because of this. As it "drys" it hardens. Deeper formations are generally softer. Some, like the Lone Mountain Mine in Nevada have faulted to the side so tunneling along the vein was very productive even though it's well below 100 feet in depth. Turquoise in this mine formed near the surface before faulting. Undoubtedly many similar formations have been lost forever due to the convolutions of the earth sending the deposits deep into the earth's crust.
Turquoise is opaque and has a Mohs scale hardness that varies remarkably. The soft, deeply mined chalks may only slightly exceed 2 on the Mohs scale to 6 for a hard, gem specimen. The hardness varies due to several factors. Environment and matrix are key. In silica, usually very minute quartz particles are present (see silicification discussed above); the stone will be hard enough for use as a gem stone. This process will strengthen some of the matrixes as well. If silicification has not occurred the turquoise will likely be chalky, porous, and soft. It will not be useble in jewelry without undergoing treatment- usually stabilization (to be discussed later.)
The specific gravity of turquoise is 2.6 to 2.8, about the same as quartz. Of course, when some minerals replace other minerals the specific gravity will change.
Color- The color of turquoise can vary from a deep blue to a deep green, with every variation of color in-between. This is due to the chemical composition of the turquoise. Generally, the more copper in the molecule the bluer the turquoise. The introduction of iron causes the greener cast to the stone. Turquoise specimens from various mines have been analyzed to determine their chemical compositions. Generally these analyses support this color change generalization. Turquoise can also change color naturally, usually toward the green. Again, the more moisture available will cause turquoise to turn toward green. This can occur in the ground or in jewelry absorbing moisture, oils, and other properties. This is not unlike blue azurite changing to green malachite as its creation environment increases its water content. Man too can change the color of turquoise artifically by submerging the stone in animal fat (done for centuries simply to make it prettier- as well as to add to its value in trade.) Wetting the stone in water immediately prior to sale makes the color more pronounced and the stone heavier- both of these techniques, however are temporary. We will discuss prominent color change later in this paper.
Remember although turquoise must consist of copper, aluminum and phosphorus. Other elements can replace various percentages of these and thereby change the molecular structure. For example, two very rare minerals, chalcosiderite (where iron replaces the aluminum) and faustite (where zinc replaces the aluminum) do exist in turquoise environments. However, more frequently there will be a partial replacemet of the aluminum with iron and zinc, thus leaving turquoise altered only in color, specific gravity and of course, chemical composition. Most turquoise is concentrated near the copper-aluminum end of this spectrum then toward the iron or zinc-aluminum end. Therefore, most turquoise is blue or blue-green then green or green-blue as would be the case if iron would be more prevalent. The following may shed some light on the vast differences in the molecular structure of turquoise. A great many variables can and do exist in this stone and it is sill turquoise. No one factor makes it more or less valuable.
A series of chemical tests were conducted on the turquoise from 21 different mines in several countires. There were marked differences in the composition of the oxides forming the turquoise in these tests. For example: Copper reflected a low of 1.4% in a Persian mine to a high a 9% in Virginia; Phosphorus was low at 14% in the Persian test and 39% in Jordan; Aluminum varied from a low of 29% in New Mexico's Cerillos mine to a high of 54% in Jordan. There were 10 U.S. samples. They averaged: Copper, 4%-9%, Phosphorus, 27%-34% and Aluminum, 29%-44%. The tests for iron ranged from none in three mines to 7.8% in Persia. U.S. mines ranged from 1.2% to 4.4%. Water, a key element of course, averaged 18% in all mines. (This is information from Pogue. [Ref. #1])
These tests, if nothing else, show just how complex a mined turquoise is. It simply does not always follow the accepted generalizations. An example of this is that the tests show that a Persian mine noted for its blue turquoise had the lowest copper and highest iron content. This appears to contradict the generalization that bluer stones contain more copper. The tests did reveal traces of other oxides and these too have an effect on color. Lastly, these tests were conducted many years ago and we know today that ore samples from a single mine can vary rather markedly.
Natural, Stabilized, Treated, Fake and Synthetic Turquoise
We will discuss these various types as they relate to the jewelry industry.
NATURAL- This turquoise comes directly from the mine. It is cut, shaped, polished and set into jewelry. Perhaps it had only been drilled and polished and suspended on a necklace. In any event the stone has had no man-made treatment or additives other than the polishing compounds to set off its luster. Most stones used in their natural state are very good to gem quality. In other words, hard and dense with an inherent luster that does not lessen as it is exposed to its natural setting.
STABILIZED- This is a natural turquoise, usually in nugget form, that is too porous or soft to hold a luster. It is therefore submerged into a stabilizing compound, frequently an epoxy resin. The natural capillary action of the porous stone draws this stabilizing compound throughout the stone. It is then dried. When it is thoroughly dried it can be cut, drilled, cabbed, etc. and prepared for jewelry. Please note that the turquoise has not been altered. The pores of the stone have been filled with a clear resin that makes the stone usable. If this type of turquoise were not on the market, many, many jewelry artisans would not be employed. It allows wide diversity. For example, necklaces of tiny turquoise beads now can be made and tiny inlay is possible. Colors will not change because the pores are sealed. It is not practical to use a high-grade natural stone for heishe. For example, too much turquoise is wasted in the grinding and the resultant bead will be fragile and will eventually change color as well.
On the other hand, some stabilizing compounds can have color added. This causes the turquoise to assume a color that is not naturally inherent to that stone. This is referred to as "color shot" or "color stabilized", the latter is misleading because it infers that it is the natural color which is "stabilized." This of course is not true, color has been added. This is not necessarily bad, as jewelry making is art, this color enhancement can imporve the appearance of the piece. It goes without saying that the value is less than if the turquoise was naturally the color desired.
TREATED- This form of color enhancement has existed for thousands of years. In Pogue's excellent treatise he discusses writings on this subject that pre-date Christ. A common way is to submerge the stone in any animal or vegetable oil and later air dry it. It will have a luster that did not previously exist. This will not last for a very long time and the likelihood of oil stains when being worn caused the seller to leave the area shortly after the sale. Even today turquoise mechants submerge the stone in water, it enhances the color and makes it weigh more.
FAKE and SYNTHETIC Turquoise- People have been faking turquoise for centuries using ceramics, bone, color-enhanced minerals, and more recently, celluloid and plastic, among other things. This is not much of a problem now as people are simply too familiar with turquoise. However, synthetic turquoise, frequently chemically perfect, has appeared on the market in some quantity. This is literaly stove-top turquoise. It has a very natural matrix created by placing stones in the "batter" or sprinkling in pyrite, etc. When the mix is cut then cabbed these foreign additives, which are real, add to the illusion that the entire stone is natural. Synthetics become fake if not properly identified.
One could write pages on this and still not cover the subject. In the earliest of times, up to the late 1800's, certainly the pure blue without matrix was considered the best. It was time tested, if the color did not change it was of "the old rock", in other words... gem! If it changed color it was "the new rock", inferior and not of permanent color. While the pure blue stone could be of gem quality the matrixed stone was not considered a gem stone. This all changed in the late 19th century. The American Indian preferred the matrixed stone and so an entire new grading criteria evolved.
Today, the preferred turquoise in the Middle East is still the pure blue. As such, great quantities of rather inferior stabilized "chalk" turquoise has been shipped there for sale to local jewelers and merchants. I've had people bring me pieces they bought in bazaars and markets as old Persian or Arab jewelry that were made from Kingman stabilized turquoise... BEWARE...
GRADING TURQUOISE in the U.S.
1) Hardness of Density. . . This is a critical feature in determining the grade of a turquoise specimen. An inferior chalk-like turquoise will feel light, it will be porous and it will stick to your tongue. The harder, denser pieces will have a "good" substantive feel to them. They will not draw the quantity of moisture from your tounge that lower grades will but some adhesion to your tounge will be felt. As it's density increases so too does its hardness. As turquoise can vary from a little over 2 to nearly 6 on the Mohs scale, the specific gravity will also vary, the usual being 2.8, similar to that of quartz.
2) Luster... it should come from within the stone not just a surface polish.
3) Color...No area is less codified than this. The ancients preferred blue because a gem-grade blue stone would not change color (King Tut's treasures include a substantial amount of blue turquoise -- it appears today unchanged). As the less hard blues would eventually shade towards green, it was assumed that green was not as good. Time has proven this wrong. Some green hued turquoise such as Skyhorse, China Mountain (both are names given to tourquoise from China), Cerillos, Blue Gem, Fox, to name a few are ranked in the top three grades (see below) are as many blues, ie. Lander, Lone Mountain, Red Mountain, Morenci, Bisbee, etc. And to make matters even more difficult some mining areas such as Skyhorse, China Mountain, Blue Gem, and Royston produce both colors.
4) Matrix.. This is the host rock in which the turquoise forms and bonds. When cut, the host rock and the turquoise are one piece. The pattern of this matrix must be pleasing. This is subjective at best but with experience one learns what most people believe to be the most desirable. Again, as in color, the opinions on which matrix is "best" varies dramaically. There are hard core supporters of a fine, dark spiderweb as in the Lander, Number Eight, Lone Mountain, Red Mountain, Skyhorse, and China Mountain mines. The heavy brown black matrix of Bisbee and Tyrone have their followers as the world's best. A hard, lustrous cabochon from Morenci typifies another beautiful and highly regarded matrix. It is free form with a blending of webbing and deep pattern matrix combined with visible pyrite inclusions.
In a given cabochon of turquoise any of the above could qualify as "best" depending on the personal preferences of the one judging. However, when mounted in jewelry then the balance of the turquoise in the setting by itself or in combination with other stones is an imprtant consideration.
5) Rarity...People covet that which is rare and the value escalates accordingly. A stone from a mine that produced a highly collectible stone that has subseqently closed has more appeal to a collector then a stone from an active mine. Again, factors 1,2,3,4 above MUST also apply. The rarity factor is simply the price descriminator. Example -- A beautiful five carat cabochon of deep blue turquoise with a tiny black spider web matrix from the Lander Mine, Nevada (closed many years ago) has a retail value of $300.00 to $500.00. A similar cabochon from the Lone Mountain Mine, also closed, would be $200.00 to $300.00. It is every bit as good and in the case of the matrix better, but it produced for a longer time. A similar cabochon from teh "Skyhorse Mine" a term used to identify a superior grade of turquoise from Tibet and China would be nearer $50.00 because it is still active and the turquoise has yet to be properly publicized.
GRADES Again, a subjective area but the following are accepted by a good many in the trade:
1) Gem: For a stone to be considered a gem all of the above criteria must be met except the rarity factor. Less then 1% of all turquoise can be legitimately called Gem. Remember- rarity affects value, not natural quality.
2) Very High Grade: Stones of this grade are nearly perfect and exhibit the same general characteristics as gem escept that the matrix patterns may not be perfectly balanced but the stone would still be quite hard and quite lusterous. About 3% of all turquoise is very high grade.
3) High Grade: Turquoise of this grade is used in most high but not competition quality jewelry. It is hard but "as hard," balanced but not perfect, a very attractive specimen that could be just a bit better. Luster must be perfect. About 5% of turquoise fits this grade.
4) a)Jewelry Quality b) High Quality c) Investment Quality
NOTE: Word "grades" is omitted.
It should have a good hardness, a good feel, and be hard enough not to need stabilization. It must have a nice luster but not necessarily be as deep as in 1-3 above. Matrix pattern should be attractive but probably a bit unbalanced. This stone could be stabilized to prevent any color change but it is not necessary to do so as it will change slowly and remain attractive none the less. Approximately 10% of turquoise is in this category.
5) a) Mine Run b) Average Quality c) Good Quality d) Stock
This is a very average turquoise that doesn't have to be stabilized as it will hold a polish and it will be attractive. Stabilizing however, strengthens it for carving and permanence. We estimate that about 20% of turquoise is in this category. In these areas stabilizing improves the stone.
6) a) Chalk b) Bulk c) Chip Stock d) "Levarite" (as in leave it right there)
Soft, porous, brittle, of little value to the jewelry industry until stabilized. Frequently insufficient color exists so "color enhancing" or "color shooting" is used, i.e. the turquoise is artificially colored. Most turquoise is in this category. One reason is, mines are going deeper into the earth and the further down one goes the lower the quality of turquoise. NOTE: The above percentage should not be taken as exact. They are a "best guess" based on this writer's experiences over 25 years in the trade.
Midi "Eternal Love" is
used with artists permission
and is copyright © 1999 Elan Michaels
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