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Turquoise

2007 Schools Wikipedia Selection. Related subjects: Mineralogy

   Turquoise
   Turquoise pebble, one inch (2.5 cm) long. This pebble is greenish and
   therefore low grade
   General
   Category Mineral
   Chemical formula CuAl[6](PO[4])[4](OH)[8]·5H[2]O
   Identification
   Colour Blue, blue-green, green
   Crystal habit Massive, nodular
   Crystal system Triclinic
   Cleavage Good to perfect - usually N/A
   Fracture Conchoidal
   Mohs Scale hardness 5-6
   Luster Waxy to subvitreous
   Refractive index 1.61-1.65
   Birefringence +0.040
   Streak Bluish white
   Specific gravity 2.6-2.9
   Fusibility Fusible in heated HCl
   Solubility Soluble in HCl

   Turquoise (or turquois) is opaque, blue-to-green hydrated copper
   aluminium phosphate mineral according to the chemical formula
   CuAl[6](PO[4])[4](OH)[8]·5H[2]O. It is rare and valuable in finer
   grades and has been enjoyed 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 had its popularity undermined 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 colour, however, has been employed
   extensively in the decorative tiles adorning Turkish places of worship
   and homes for hundreds of years, beginning with the Seljuks, and the
   association quite possibly has caused the name to take root.

Properties of turquoise

   Even the finest of turquoise is fracturable, reaching a maximum
   hardness of just under 6, or slightly more than window glass.
   Characteristically a cryptocrystalline mineral, turquoise almost never
   forms single crystals and all of its properties are highly variable.
   Its crystal system is proven to be triclinic via X-ray diffraction
   testing. With lower hardness comes lower specific gravity (high 2.90,
   low 2.60) and greater porosity: These properties are dependent on grain
   size. The lustre of turquoise is typically waxy to subvitreous, and
   transparency is usually opaque, but may be semitranslucent in thin
   sections. Colour is as variable as the mineral's other properties,
   ranging from white to a powder blue to a sky blue, and from a
   blue-green to a yellowish green. The blue is attributed to
   idiochromatic copper while the green may be the result of either iron
   impurities (replacing aluminium) or dehydration.

   The refractive index (as measured by sodium light, 589.3 nm) of
   turquoise is approximately 1.61 or 1.62; this is a mean value seen as a
   single reading on a gemmological refractometer, owing to the almost
   invariably polycrystalline nature of turquoise. A reading of 1.61–1.65
   ( birefringence 0.040, biaxial positive) has been taken from rare
   single crystals. An absorption spectrum may also be obtained with a
   hand-held spectroscope, revealing a line at 432 nanometres and a weak
   band at 460 nanometres (this is best seen with strong reflected light).
   Under longwave ultraviolet light, turquoise may occasionally fluoresce
   green, yellow or bright blue; it is inert under shortwave ultraviolet
   and X-rays.

   Turquoise is infusible in all but heated hydrochloric acid. Its streak
   is a pale bluish white and its fracture is conchoidal, leaving a waxy
   lustre. Despite its low hardness relative to other gems, turquoise
   takes a good polish. Turquoise may also be peppered with flecks of
   pyrite or interspersed with dark, spidery limonite veining.

Formation

   As a secondary mineral, turquoise apparently forms by the action of
   percolating acidic aqueous solutions during the weathering and
   oxidation of pre-existing minerals. For example, the copper may come
   from primary copper sulfides such as chalcopyrite or from the secondary
   carbonates malachite or azurite; the aluminium may derive from
   feldspar; and the phosphorus from apatite. Climate factors appear to
   play an important role as turquoise is typically found in arid regions,
   filling or encrusting cavities and fractures in typically highly
   altered volcanic rocks, often with associated limonite and other iron
   oxides. In the American southwest turquoise is almost invariably
   associated with the weathering products of copper sulfide deposits in
   or around potassium feldspar bearing porphyritic intrusives. In some
   occurrences alunite, potassium aluminium sulfate, is a prominent
   secondary mineral. Typically turquoise mineralization is restricted to
   a relatively shallow depth of less than 20 m, although it does occur
   along deeper fracture zones where secondary solutions have greater
   penetration.

   Although the features of turquoise occurrences are consistent with a
   secondary or supergene origin, some sources refer to a hypogene origin.
   The hypogene hypothesis, which holds that the aqueous solutions
   originate at significant depth, from hydrothermal processes. Initially
   at high temperature, these solutions rise upward to surface layers,
   interacting with and leaching essential elements from pre-existing
   minerals in the process. As the solutions cool, turquoise precipitates,
   lining cavities and fractures within the surrounding rock. This
   hypogene process is applicable to the original copper sulfide
   deposition; however, it is difficult to account for the many features
   of turquoise occurrences by a hypogene process. That said, there are
   reports of two phase fluid inclusions within turquoise grains that give
   elevated homogenization temperatures of 90 to 190 ^oC that require
   explanation.

   Turquoise is nearly always cryptocrystalline and massive and assumes no
   definite external shape. Crystals, even at the microscopic scale, are
   exceedingly rare. Typically the form is vein or fracture filling,
   nodular, or botryoidal in habit. Stalactite forms have been reported.
   Turquoise may also pseudomorphously replace feldspar, apatite, other
   minerals, or even fossils. Odontolite is fossil bone or ivory that has
   been traditionally thought to have been altered by turquoise or similar
   phosphate minerals such as the iron phosphate vivianite. Intergrowth
   with other secondary copper minerals such as chrysocolla is also
   common.

Occurrence

   Massive turquoise in matrix with quartz from Mineral Park, Arizona.
   Enlarge
   Massive turquoise in matrix with quartz from Mineral Park, Arizona.

   Turquoise was among the first gems to be mined, and while many historic
   sites have been depleted, some are still worked to this day. These are
   all small-scale, often seasonal operations, owing to the limited scope
   and remoteness of the deposits. Most are worked by hand with little or
   no mechanization. However, turquoise is often recovered as a byproduct
   of large-scale copper mining operations, especially in the United
   States.

Iran

   For at least 2,000 years, the region once known as Persia, has remained
   the most important source of turquoise, for it is here that fine
   material is most consistently recovered. This "perfect colour" deposit
   is restricted to a mine-riddled, 2,012-metre mountain peak of
   Ali-mersai, 25 km 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 (3,000 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

   A selection of Ancestral Puebloan (Anasazi) turquoise and orange
   argillite inlay pieces from Chaco Canyon (dated ca. 1020–1140 CE) show
   the typical colour range and mottling of American turquoise.
   Enlarge
   A selection of Ancestral Puebloan (Anasazi) turquoise and orange
   argillite inlay pieces from Chaco Canyon (dated ca. 1020–1140 CE) show
   the typical colour range and mottling of American turquoise.
   Bisbee turquoise commonly has a hard chocolate brown colored matrix,
   and is considered some of the finest in the world.
   Enlarge
   Bisbee turquoise commonly has a hard chocolate brown colored matrix,
   and is considered some of the finest in the world.

   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 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 an estimated 75–100 mines opened over the
   state's history. The Nevada material is noted for its often attractive
   brown or black limonite veining, producing what is called "spiderweb
   matrix".

   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, most 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).

History of use

   Trade in turquoise crafts, such as this freeform pendant dating from
   1000–1040 CE, is believed to have brought the Ancestral Puebloans of
   the Chaco Canyon great wealth.
   Enlarge
   Trade in turquoise crafts, such as this freeform pendant dating from
   1000–1040 CE, is believed to have brought the Ancestral Puebloans of
   the Chaco Canyon great wealth.

   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 Muhgal 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 jewellery 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.
   The iconic gold burial mask of Tutankhamun, inlaid with turquoise,
   lapis lazuli, carnelian and coloured glass.
   Enlarge
   The iconic gold burial mask of Tutankhamun, inlaid with turquoise,
   lapis lazuli, carnelian and coloured glass.

   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.

   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 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; others disagree, however, translating
   the stones to be jacinth ( zircon) and agate respectively. Scholars
   also disagree as to which tribes each stone is meant to represent.

Imitations

   The Egyptians were apparently 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.
   Some natural blue to blue-green materials, such as this botryoidal
   chrysocolla with quartz drusy, are occasionally confused with, or used
   to imitate turquoise.
   Some natural blue to blue-green materials, such as this botryoidal
   chrysocolla with quartz drusy, are occasionally confused with, or used
   to imitate turquoise.

   The most common imitation of turquoise encountered today is dyed
   howlite and magnesite, both white in their natural states, and the
   former also having natural (and convincing) black veining similar to
   that of turquoise. Dyed chalcedony, jasper, and marble is less common,
   and much less convincing. Other natural materials occasionally confused
   with or used in lieu of turquoise include: variscite; faustite;
   chrysocolla (especially when impregnating quartz); lazulite;
   smithsonite; hemimorphite; wardite; and a fossil bone or tooth called
   odontolite or "bone turquoise", coloured blue naturally by the mineral
   vivianite. While rarely encountered today, odontolite was once mined in
   large quantities—specifically for its use as a substitute for
   turquoise—in southern France.

   These fakes are detected by gemmologists using a number of tests,
   relying primarily on non-destructive, close examination of surface
   structure under magnification; a featureless, pale blue background
   peppered by flecks or spots of whitish material is the typical surface
   appearance of natural turquoise, while manufactured imitations will
   appear radically different in both colour (usually a uniform dark blue)
   and texture (usually granular or sugary). Glass and plastic will have a
   much greater translucency, with bubbles or flow lines often visible
   just below the surface. Staining between grain boundaries may be
   visible in dyed imitations.

   Some destructive tests may, however, be necessary; for example, the
   application of diluted hydrochloric acid will cause the carbonates
   odontolite and magnesite to effervesce and howlite to turn green, while
   a heated probe may give rise to the acrid smell so indicative of
   plastic. Differences in specific gravity, refractive index, light
   absorption (as evident in a material's absorption spectrum), and other
   physical and optical properties are also considered as means of
   separation. Imitation turquoise is so prevalent that it likely
   outnumbers real turquoise by a wide margin. Even material used in
   authentic Native American and Tibetan jewellery is often fake or, at
   best, heavily treated.

Treatments

   Turquoise is treated to enhance both its colour and durability (i.e.,
   increased hardness and decreased porosity). Historically, light waxing
   and oiling were the first treatments to be used (since ancient times),
   providing a wetting effect (thereby enhancing the colour and lustre);
   this treatment is more or less acceptable by tradition, and because
   such material is usually of a higher grade to begin with. Conversely,
   the later development of pressure impregnation of otherwise unsaleable
   chalky American material by epoxy and plastics (such as polystyrene)
   and water glass—also producing a wetting effect in addition to
   improving durability—are rejected by some as too radical an alteration.
   Plastic and water glass are technologically superior to oil and wax in
   that the former treatment are far more permanent and stable, and can be
   applied to material too friable for oil or wax to be of sufficient
   help; such material is termed "bonded" or "stabilized" turquoise. 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 impregnation most American mining operations would be
   unprofitable.

   Oiled and waxed stones are also 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.) Likewise, 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 purists—especially since some dyes may fade or rub off on
   the wearer. Dyes have also been used to darken the veins of turquoise.
   Perhaps the most radical of treatments is "reconstitution", wherein
   supposedly fragments of fine material too small to be used singly are
   powdered and then bonded to form a solid mass. Much (if not all) of
   this "reconstituted" material is likely a complete fabrication (with no
   natural components), or may have foreign filler material added to it
   (see Imitations section). 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.

   As the 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
   are termed doublets and can be very deceptive in certain jewellery
   setting styles (such as closed back and bevel settings). Some turquoise
   is cut with the mother rock serving as a base; these are usually not
   considered doublets but may have an intrinsic value lower than that of
   "whole" stones. Doublets, like the aforementioned treatments, are legal
   provided they are disclosed to the customer before sale.

   As is so often with gems, full disclosure is frequently not given; it
   is therefore left to gemmologists 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.

Valuation and care

   Slab of turquoise in matrix showing a large variety of different
   colouration
   Enlarge
   Slab of turquoise in matrix showing a large variety of different
   colouration

   Richness of colour is the chief determiner of value in turquoise;
   generally speaking, the most desirable is a strong sky to "robin's egg"
   blue (in reference to the eggs of the American Robin); value decreases
   with the increase of green hue, lightening of colour, and mottling. 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 complimentary, 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 complimentary 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 hairspray, 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
   box to avoid scratching by harder gems. Also, make sure the box is not
   airtight, or the turquoise will become ruined.

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