AskDefine | Define turquoise

Dictionary Definition

turquoise

Noun

1 a blue to gray green mineral consisting of copper aluminum phosphate; blue turquoise is valued as a gemstone
2 a shade of blue tinged with green [syn: greenish blue, aqua, aquamarine, cobalt blue, peacock blue]

User Contributed Dictionary

English

Etymology

From turkeis, from turqueise. The stone was originally brought to Europe from Turkestan.

Noun

  1. A sky-blue, greenish-blue, or greenish-gray semi-precious gemstone.
  2. A pale greenish-blue colour, like that of the gemstone.
    turquoise colour:   

Derived terms

Translations

gemstone
colour

Adjective

  1. Made of turquoise (the gemstone).
  2. Having a pale greenish-blue colour.

Translations

made of turquoise
  • Bosnian: tirkizan
  • Croatian: tirkizan
  • Italian: di turchese m|f
  • Russian: бирюзовый
having a pale greenish-blue colour

See also

French

Noun

fr-noun f
  1. turquoise (gemstone)

Noun

fr-noun m
  1. turquoise (colour)

Adjective

turquoise (invariable)
  1. turquoise-colored.

Extensive Definition

Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula CuAl6(PO4)4(OH)8·4H2O. It is rare and valuable in finer grades and has been prized as a gem and ornamental stone for thousands of years owing to its unique hue. In recent times turquoise, like most other opaque gems, has been devalued by the introduction of treatments, imitations, and synthetics onto the market, some difficult to detect even by experts.
The substance has been known by many names, but the word turquoise was derived around 16th century from the French language either from the word for Turkish (Turquois) or dark-blue stone (pierre turquin). This may have arisen from a misconception: turquoise does not occur in Turkey but was traded at Turkish bazaars to Venetian merchants who brought it to Europe. the 2,012-metre mountain peak of Ali-mersai, which is tens of kilometers from Mashhad, the capital of Khorasan province, Iran. A weathered and broken trachyte is host to the turquoise, which is found both in situ between layers of limonite and sandstone, and amongst the scree at the mountain's base. These workings, together with those of the Sinai Peninsula, are the oldest known.
Iranian turquoise is often found replacing feldspar. Although it is commonly marred by whitish patches, its colour and hardness are considered superior to the production of other localities. Iranian turquoise has been mined and traded abroad for centuries, and was probably the source of the first material to reach Europe.

Sinai

Since at least the First Dynasty (3000 BCE), and possibly before then, turquoise was used by the Egyptians and was mined by them in the Sinai Peninsula, called "Country of Turquoise" by the native Monitu. There are six mines in the region, all on the southwest coast of the peninsula, covering an area of some 650 km². The two most important of these mines, from a historic perspective, are Serabit el-Khadim and Wadi Maghareh, believed to be among the oldest of known mines. The former mine is situated about 4 kilometres from an ancient temple dedicated to Hathor.
The turquoise is found in sandstone that is, or was originally, overlain by basalt. Copper and iron workings are present in the area. Large-scale turquoise mining is not profitable today, but the deposits are sporadically quarried by Bedouin peoples using homemade gunpowder. In the rainy winter months, miners face a risk from flash flooding; even in the dry season, death from the collapse of the haphazardly exploited sandstone mine walls is not unheard of. The colour of Sinai material is typically greener than Iranian material, but is thought to be stable and fairly durable. Often referred to as Egyptian turquoise, Sinai material is typically the most translucent, and under magnification its surface structure is revealed to be peppered with dark blue discs not seen in material from other localities.
In proximity to nearby Eilat, Israel, an attractive intergrowth of turquoise, malachite, and chrysocolla is found. This rock is called Eilat stone and is often referred to as Israel's national stone: it is worked by local artisans for sale to tourists.

United States

The Southwest United States is a significant source of turquoise; Arizona, California (San Bernardino, Imperial, and Inyo counties), Colorado (Conejos, El Paso, Lake, and Saguache counties), New Mexico (Eddy, Grant, Otero, and Santa Fe counties) and Nevada (Clark, Elko, Esmerelda County, Eureka, Lander, Mineral County and Nye counties) are (or were) especially rich. The deposits of California and New Mexico were mined by pre-Columbian Native Americans using stone tools, some local and some from as far away as central Mexico. Cerrillos, New Mexico is thought to be the location of the oldest mines; prior to the 1920s, the state was the country's largest producer; it is more or less exhausted today. Only one mine in California, located at Apache Canyon, operates at a commercial capacity today.
The turquoise occurs as vein or seam fillings, and as compact nuggets; these are mostly small in size. While quite fine material—rivalling Iranian material in both colour and durability—is sometimes found, most American turquoise is of a low grade (called "chalk turquoise"); high iron levels mean greens and yellows predominate, and a typically friable consistency precludes use in jewellery in the turquoise's untreated state. Arizona is currently the most important producer of turquoise by value, with the vivid Bisbee Blue being a good example of the state's natural endowment; much of the Arizona material is recovered as a byproduct of copper mining.
Nevada is the country's other major producer, with more than 120 mines which have yielded significant quantities of turquoise. Unlike elsewhere in the US, most Nevada mines have been worked primarily for their gem turquoise and very little has been recovered as a byproduct of other mining operations. Nevada turquoise is found as nuggets, fracture fillings and in breccias as the cement filling interstices between fragments. Because of the geology of the Nevada deposits, a majority of the material produced is hard and dense, being of sufficient quality that no treatment or enhancement is required. While nearly every county in the state has yielded some turquoise, the chief producers are in Lander and Esmerelda Counties. Most of the turquoise deposits in Nevada occur along a wide belt of tectonic activity that coincides with the state's zone of thrust faulting. It strikes about N15E and extends from the northern part of Elko County, southward down to the California border southwest of Tonopah. Nevada has produced a wide diversity of colours and mixes of different matrix patterns, with turquoise from Nevada coming in various shades of blue, blue-green, and green. Nevada produces some unique shades of bright mint to apple to neon yellow green. Some of this unusually coloured turquoise may contain significant zinc and iron, which is the cause of the beautiful bright green to yellow-green shades. Some of the green to green yellow shades may actually be Variscite or Faustite, which are secondary phosphate minerals similar in appearance to turquoise. A significant portion of the Nevada material is also noted for its often attractive brown or black limonite veining, producing what is called "spiderweb matrix". While a number of the Nevada deposits were first worked by Native Americans, the total Nevada turquoise production since the 1870s has been estimated at more than 600 tons, including nearly 400 tons from the Carico Lake mine. In spite of increased costs, small scale mining operations continue at a number of turquoise properties in Nevada, including the Godber, Orvil Jack and Carico Lake Mines in Lander County, the Pilot Mountain Mine in Mineral County, and several properties in the Royston and Candelaria areas of Esmerelda County. In 1912, the first deposit of distinct, single-crystal turquoise was discovered in Lynch Station, Campbell County, Virginia. The crystals, forming a druse over the mother rock, are very small; 1 mm (0.04 inches) is considered large. Until the 1980s Virginia was widely thought to be the only source of distinct crystals; there are now at least 27 other localities. The specimens are highly valued by collectors.
In an attempt to recoup profits and meet demand, some American turquoise is treated or enhanced to a certain degree. These treatments include innocuous waxing and more controversial procedures, such as dyeing and impregnation (see Treatments). There are however, some American mines which produce materials of high enough quality that no treatment or alterations are required. Any such treatments which have been performed should be disclosed to the buyer on sale of the material.

Other sources

China has been a minor source of turquoise for 3,000 years or more. Gem-quality material, in the form of compact nodules, is found in the fractured, silicified limestone of Yunxian and Zhushan, Hubei province. Additionally, Marco Polo reported turquoise found in present-day Sichuan. Most Chinese material is exported, but a few carvings worked in a manner similar to jade exist. In Tibet, where green turquoise has long been appreciated, gem-quality deposits purportedly exist in the mountains of Derge and Nagari-Khorsum in the east and west of the region respectively.
Other notable localities include: Afghanistan; Australia (Victoria and Queensland); northern Chile (Chuquicamata); Cornwall; Saxony; Silesia; and Turkestan.

History of its use

The pastel shades of turquoise have endeared it to many great cultures of antiquity: it has adorned the rulers of Ancient Egypt, the Aztecs (and possibly other Pre-Columbian Mesoamericans), Persia, Mesopotamia, the Indus Valley, and to some extent in ancient China since at least the Shang Dynasty. Despite being one of the oldest gems, probably first introduced to Europe (through Turkey) with other Silk Road novelties, turquoise did not become important as an ornamental stone in the West until the 14th century, following a decline in the Roman Catholic Church's influence which allowed the use of turquoise in secular jewellery. It was apparently unknown in India until the Mughal period, and unknown in Japan until the 18th century. A common belief shared by many of these civilizations held that turquoise possessed certain prophylactic qualities; it was thought to change colour with the wearer's health and protect him or her from untoward forces.
The Aztecs inlaid turquoise, together with gold, quartz, malachite, jet, jade, coral, and shells, into provocative (and presumably ceremonial) mosaic objects such as masks (some with a human skull as their base), knives, and shields. Natural resins, bitumen and wax were used to bond the turquoise to the objects' base material; this was usually wood, but bone and shell were also used. Like the Aztecs, the Pueblo, Navajo and Apache tribes cherished turquoise for its amuletic use; the latter tribe believe the stone to afford the archer dead aim. Among these peoples turquoise was used in mosaic inlay, in sculptural works, and was fashioned into toroidal beads and freeform pendants. The Ancestral Puebloans (Anasazi) of the Chaco Canyon and surrounding region are believed to have prospered greatly from their production and trading of turquoise objects. The distinctive silver jewelry produced by the Navajo and other Southwestern Native American tribes today is a rather modern development, thought to date from circa 1880 as a result of European influences.
In Persia, turquoise was the de facto national stone for millennia, extensively used to decorate objects (from turbans to bridles), mosques, and other important buildings both inside and out, such as the Medresseh-I Shah Husein Mosque of Isfahan. The Persian style and use of turquoise was later brought to India following the establishment of the Mughal Empire there, its influence seen in high purity gold jewellery (together with ruby and diamond) and in such buildings as the Taj Mahal. Persian turquoise was often engraved with devotional words in Arabic script which was then inlaid with gold.
Cabochons of imported turquoise, along with coral, was (and still is) used extensively in the silver and gold jewellery of Tibet and Mongolia, where a greener hue is said to be preferred. Most of the pieces made today, with turquoise usually roughly polished into irregular cabochons set simply in silver, are meant for inexpensive export to Western markets and are probably not accurate representations of the original style.
The Egyptian use of turquoise stretches back as far as the First Dynasty and possibly earlier; however, probably the most well-known pieces incorporating the gem are those recovered from Tutankhamun's tomb, most notably the Pharaoh's iconic burial mask which was liberally inlaid with the stone. It also adorned rings and great sweeping necklaces called pectorals. Set in gold, the gem was fashioned into beads, used as inlay, and often carved in a scarab motif, accompanied by carnelian, lapis lazuli, and in later pieces, coloured glass. Turquoise, associated with the goddess Hathor, was so liked by the Ancient Egyptians that it became (arguably) the first gemstone to be imitated, the fair semblance created by an artificial glazed ceramic product known as faience. (A similar blue ceramic has been recovered from Bronze Age burial sites in the British Isles.)
The French conducted archaeological excavations of Egypt from the mid-19th century through the early 20th. These excavations, including that of Tutankhamun's tomb, created great public interest in the western world, subsequently influencing jewellery, architecture, and art of the time. Turquoise, already favoured for its pastel shades since c. 1810, was a staple of Egyptian Revival pieces. In contemporary Western use, turquoise is most often encountered cut en cabochon in silver rings, bracelets, often in the Native American style, or as tumbled or roughly hewn beads in chunky necklaces. Lesser material may be carved into fetishes, such as those crafted by the Zuni. While strong sky blues remain superior in value, mottled green and yellowish material is popular with artisans. In Western culture, turquoise is also the traditional birthstone for those born in the month of December.

In Judeo-Christian scripture

Turquoise may have significance in Judeo-Christian scripture: In the Book of Exodus, the construction of a "breastplate of judgment" is described as part of the priestly vestments of Aaron (Exodus 28:15–30). Attached to the ephod, the breastplate (Hoshen) was adorned with twelve gemstones set in gold and arranged in four rows, each stone engraved with the name of one of the Twelve Tribes of Israel. Of the four stones in the third row, the first and second have been translated to be turquoise by various scholars and English bible versions (usually not having both as turquoise at the same time); many others disagree, however.
In regard to the first of these stones, the translation is based on the Septuagint rendering the identity of the stone as chrysolithos (the masoretic text calls it tarshish, which just refers to Tarshish, a place, and gives no clue to the gem in question); at the time it was written chrysolithos did not mean Chrysolite specifically, but only golden stone (chryso-lithos). Chrysolithos is considered by scholars to possibly mean Topaz, Chrysolite, yellow Jasper, yellow Serpentine, or Turquoise - the last of these on the basis that Turquoise contains golden flecks, and that targums identified the stone as being sea coloured. Scholars favour stones which are mostly yellow as being the more likely solution, and opaque stones (Jasper or Serpentine) as more likely than translucent ones, on the consideration of nearby stones in the Hoshen.
In regard to the second of these stones, the masoretic text calls it shoham, and the Septuagint calls it Beryllios (Beryl), though elsewhere it translates shoham as onychion (Onyx), or as smaragdos (green stone). Shoham is of uncertain meaning. Following the Septuagint, some people think the stone should be an onyx (and many more traditional English versions of the Bible take this translation), but scholars think that the stone is actually Malachite (because it is green like beryl and smaragdos, cloudy as beryl can be, and in bands like onyx).
Scholars also disagree as to which tribes of the Israelites each stone is meant to represent; traditional sources are in just as much disagreement.

Imitations

The Egyptians were the first to produce an artificial imitation of turquoise, in the glazed earthenware product faience. Later glass and enamel were also used, and in modern times more sophisticated ceramics, porcelain, plastics, and various assembled, pressed, bonded, and sintered products (composed of various copper and aluminium compounds) have been developed: examples of the latter include "Viennese turquoise", made from precipitated aluminium phosphate coloured by copper oleate; and "neolith", a mixture of bayerite and copper phosphate. Most of these products differ markedly from natural turquoise in both physical and chemical properties, but in 1972 Pierre Gilson introduced one fairly close to a true synthetic (it does differ in chemical composition owing to a binder used, meaning it is best described as a simulant rather than a synthetic). Gilson turquoise is made in both a uniform colour and with black "spiderweb matrix" veining not unlike the natural Nevada material. Turquoise is treated to enhance both its colour and durability (i.e., increased hardness and decreased porosity). As is so often the case with any precious stones, full disclosure about treatment is frequently not given. It is therefore left to gemologists to detect these treatments in suspect stones using a variety of testing methods—some of which are necessarily destructive. For example, the use of a heated probe applied to an inconspicuous spot will reveal oil, wax, or plastic treatment with certainty.

Waxing and Oiling

Historically, light waxing and oiling were the first treatments used in ancient times, providing a wetting effect, thereby enhancing the colour and lustre. This treatment is more or less acceptable by tradition, especially because treated turquoise is usually of a higher grade to begin with. Oiled and waxed stones are prone to "sweating" under even gentle heat or if exposed to too much sun, and they may develop a white surface film or bloom over time. (With some skill, oil and wax treatments can be restored.)

Stabilization

Material treated with plastic or water glass is termed "bonded" or "stabilized" turquoise. This process consists of pressure impregnation of otherwise unsaleable chalky American material by epoxy and plastics (such as polystyrene) and water glass to produce a wetting effect and improve durability. Plastic and water glass treatments are far more permanent and stable than waxing and oiling, and can be applied to material too chemically or physically unstable for oil or wax to provide sufficient improvement. Conversely, stabilization and bonding are rejected by some as too radical an alteration.
The epoxy binding technique was first developed in the 1950s and has been attributed to Colbaugh Processing of Arizona, a company that still operates today. The majority of American material is now treated in this manner although it is a costly process requiring many months to complete. Without such impregnation, most American mining operations would be unprofitable.

Dyeing

The use of Prussian blue and other dyes (often in conjunction with bonding treatments) to "enhance" – that is, make uniform or completely change – colour is regarded as fraudulent by some purists, especially since some dyes may fade or rub off on the wearer. Dyes have also been used to darken the veins of turquoise.

Reconstitution

Perhaps the most radical of treatments is "reconstitution", wherein fragments of fine turquoise material, too small to be used individually, are powdered and then bonded to form a solid mass. Much, if not all, of this "reconstituted" material is likely artificial with no natural components, or may have foreign filler material added to it (see Imitations section).

Zachery Processing

Another treatment—the details of which remain undisclosed—is the so-called Zachery Process, named after its developer, electrical engineer and turquoise trader James E. Zachery. This process claims to use only medium grade material at a minimum, leaving the turquoise harder and with a better colour and lustre.

Backing

Since finer turquoise is often found as thin seams, it may be glued to a base of stronger foreign material as a means of reinforcement. These stones are termed "Backed" and it is standard practice that all thinly cut turquoise in the Southwestern United States is backed. Native indigenous peoples of this region, because of their considerable use and wearing of turquoise, found that backing increased the durability of thinly cut slabs and cabs of turquoise. They observed that if the stone was not backed it would, for the most part, end up cracking. Early backing materials were the casings of old model T batteries and progressed to old phonograph records and most recently to the use of epoxy steel resins. Backing of turquoise is not known outside of the Native American and Southwestern United States jewelry trade. The value of turquoise of the highest quality is not discounted because it is backed and indeed the process is expected for most thinly cut American commercial gemstones.

Valuation and care

Hardness and richness of colour are two of the major factors in determining the value of turquoise; while colour is a matter of individual taste, generally speaking, the most desirable is a strong sky to "robin's egg" blue (in reference to the eggs of the American Robin). In Tibet, however, a greener blue is said to be preferred. Whatever the colour, turquoise should not be excessively soft or chalky; even if treated, such lesser material (to which most turquoise belongs) is liable to fade or discolour over time and will not hold up to normal use in jewellery.
The mother rock or matrix in which turquoise is found can often be seen as splotches or a network of brown or black veins running through the stone in a netted pattern; this veining may add value to the stone if the result is complementary, but such a result is uncommon. Such material is sometimes described as "spiderweb matrix"; it is most valued in the Southwest United States and Far East, but is not highly appreciated in the Near East where unblemished and vein-free material is ideal (regardless of how complementary the veining may be). Uniformity of colour is desired, and in finished pieces the quality of workmanship is also a factor; this includes the quality of the polish and the symmetry of the stone. Calibrated stones—that is, stones adhering to standard jewellery setting measurements—may also be more sought after. Like coral and other opaque gems, turquoise is commonly sold at a price according to its physical size in millimetres rather than weight.
Turquoise is treated in many different ways, some more permanent and radical than others. Controversy exists as to whether some of these treatments should be acceptable, but one can be more or less forgiven universally: This is the light waxing or oiling applied to most gem turquoise to improve its colour and lustre; if the material is of high quality to begin with, very little of the wax or oil is absorbed and the turquoise therefore does not "rely" on this impermanent treatment for its beauty. All other factors being equal, untreated turquoise will always command a higher price. Bonded and "reconstituted" material is worth considerably less.
Being a phosphate mineral, turquoise is inherently fragile and sensitive to solvents; perfume and other cosmetics will attack the finish and may alter the colour of turquoise gems, as will skin oils, as will most commercial jewelry cleaning fluids. Prolonged exposure to direct sunlight may also discolour or dehydrate turquoise. Care should therefore be taken when wearing such jewels: cosmetics, including sunscreen and hair spray, should be applied before putting on turquoise jewellery, and they should not be worn to a beach or other sun-bathed environment. After use, turquoise should be gently cleaned with a soft cloth to avoid a build up of residue, and should be stored in its own container to avoid scratching by harder gems. Turquoise can also be adversely affected if stored in an airtight container.

Notes

References

turquoise in Arabic: فيروز (حجر كريم)
turquoise in Catalan: Turquesa (Mineral)
turquoise in Czech: Tyrkys
turquoise in German: Türkis (Mineral)
turquoise in Estonian: Türkiis
turquoise in Spanish: Turquesa
turquoise in Esperanto: Turkiso
turquoise in Persian: فیروزه
turquoise in French: Turquoise (pierre)
turquoise in Galician: Turquesa
turquoise in Hindi: फीरोजा़
turquoise in Italian: Turchese
turquoise in Hebrew: טורקיז
turquoise in Georgian: ფირუზი
turquoise in Lithuanian: Turkis
turquoise in Hungarian: Türkiz
turquoise in Dutch: Turkoois (mineraal)
turquoise in Japanese: トルコ石
turquoise in Polish: Turkus
turquoise in Portuguese: Turquesa
turquoise in Quechua: Anqas umiña
turquoise in Russian: Бирюза
turquoise in Slovak: Tyrkys
turquoise in Finnish: Turkoosi
turquoise in Swedish: Turkos
turquoise in Vietnamese: Ngọc lam
turquoise in Turkish: Turkuaz (mineral)
turquoise in Ukrainian: Бірюза
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