Turquoise is an opaque, blue-to-green mineral that is a hydrated
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 gemstone and ornamental stone for thousands of
years owing to its unique hue. In recent times, turquoise has been
devalued, like most other opaque gems, by the introduction onto the
market of treatments, imitations and synthetics.
The gemstone has been known by many names.
Pliny the Elder
Pliny the Elder referred to
the mineral as callais and the Aztecs knew it as chalchihuitl. The
word turquoise dates to the 17th century and is derived from the
French turquois for "Turkish" because the mineral was first brought to
Europe through Turkey, from mines in the historical Khorasan Province
1 Properties of turquoise
3.3 United States
3.4 Other sources
4 History of use
5 Cultural associations
7.1 Waxing and oiling
8 Valuation and care
9 See also
11 Further reading
12 External links
Properties of turquoise
The finest of turquoise reaches a maximum Mohs 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. X-ray
diffraction testing shows its crystal system to be triclinic.
With lower hardness comes lower specific gravity (2.60–2.90) and
greater porosity; these properties are dependent on grain size. The
lustre of turquoise is typically waxy to subvitreous, and its
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 of turquoise (as measured by sodium light,
589.3 nm) is approximately 1.61 or 1.62; this is a mean value
seen as a single reading on a gemological 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 nm and a
weak band at 460 nm (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 insoluble 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.
"Big Blue", a large turquoise specimen from the copper mine at
Cananea, Sonora, Mexico
As a secondary mineral, turquoise forms by the action of percolating
acidic aqueous solutions during the weathering and oxidation of
preexisting 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
Southwestern United States
Southwestern United States 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 metres (66 feet), although it
does occur along deeper fracture zones where secondary solutions have
greater penetration or the depth to the water table is greater.
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.
Massive Kingman blue turquoise in matrix with quartz from Mineral
Park, Arizona, US
Turquoise was among the first gems to be mined, and many historic
sites have been depleted, though some are still worked to this day.
These are all small-scale operations, often seasonal 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.
Cutting and grinding turquoise in Nishapur, Iran, 1973
Iran has been an important source of turquoise for at least 2,000
years. It was initially named by Iranians "pirouzeh" meaning
"victory", and later the
Arabs called it "firouzeh".
In Iranian architecture, the blue turquoise was used to cover the
domes of palaces because its intense blue colour was also a symbol of
heaven on earth.
Persian turquoise from Iran
This deposit is blue naturally and turns green when heated due to
dehydration. It is restricted to a mine-riddled region in Nishapur,
the 2,012 m (6,601 ft) mountain peak of Ali-mersai near
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 are the oldest known, together with
those of the Sinai Peninsula.
Iran also has turquoise mines in
Since at least the
First Dynasty (3000 BCE) in ancient Egypt, and
possibly before then, turquoise was used by the
Egyptians and was
mined by them in the Sinai Peninsula. This region was known as the
Turquoise by the native Monitu. There are six mines in the
peninsula, all on its southwest coast, covering an area of some
650 km2 (250 sq mi). 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 the deity 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
A selection of Ancestral
Pueblo (Anasazi) turquoise and orange
argillite inlay pieces from Chaco Canyon, New Mexico, US (dated c.
1020–1140) show the typical colour range and mottling of American
turquoise. Some likely came from Los Cerrillos.
A fine turquoise specimen from Los Cerrillos, New Mexico, US, at the
Smithsonian Museum. Cerrillos turquoise was widely used by Native
Americans prior to the Spanish conquest.
Bisbee turquoise commonly has a hard chocolate brown coloured matrix.
Untreated turquoise, Nevada, US. Rough nuggets from the McGinness
Mine, Austin. Blue and green cabochons showing spiderweb, Bunker Hill
Southwest United States
Southwest United States is a significant source of turquoise;
California (San Bernardino, Imperial, Inyo counties),
Colorado (Conejos, El Paso, Lake, Saguache counties), New Mexico
(Eddy, Grant, Otero, Santa Fe counties) and
Nevada (Clark, Elko,
Esmeralda 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 is sometimes
found, rivalling Iranian material in both colour and durability, most
American turquoise is of a low grade (called "chalk turquoise"); high
iron levels mean greens and yellows predominate, and a typically
friable consistency in the turquoise's untreated state precludes use
Arizona is currently the most important producer of turquoise by
value. Several mines exist in the state, two of them famous for
their unique colour and quality and considered the best in the
industry: the Sleeping Beauty Mine in Globe ceased turquoise mining in
August 2012. The mine chose to send all ore to the crusher and to
concentrate on copper production due to the rising price of copper on
the world market. The price of natural untreated Sleeping Beauty
turquoise has risen dramatically since the mine's closing. The Kingman
Mine as of 2015 still operates alongside a copper mine outside of the
city. Other mines include the Blue Bird mine, Castle Dome, and Ithaca
Peak, but they are mostly inactive due to the high cost of operations
and federal regulations The
Lavender Pit mine at Bisbee
ceased operations in 1974 and never had a turquoise contractor. All
Bisbee turquoise was "lunch pail" mined. It came out of the copper ore
mine in miners' lunch pails. Morenci and
Turquoise Peak are either
inactive or depleted.
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 Esmeralda counties. Most of the turquoise
Nevada occur along a wide belt of tectonic activity that
coincides with the state's zone of thrust faulting. It strikes about
N15°E and extends from the northern part of Elko County, southward
down to the
California border southwest of Tonopah.
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. 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 in) is considered large. Until the 1980s
widely thought to be the only source of distinct crystals; there are
now at least 27 other localities.
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
Turquoise prehistoric artefacts (beads) are known since the fifth
millennium BCE from sites in the
Eastern Rhodopes in
Bulgaria - the
source for the raw material is possibly related to the nearby Spahievo
Ph-Zn ore field.
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
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,
gem-quality deposits purportedly exist in the mountains of
Nagari-Khorsum in the east and west of the region respectively.
Other notable localities include: Afghanistan;
Australia (Victoria and
Queensland); north India; northern
Chile (Chuquicamata); Cornwall;
Saxony; Silesia; and Turkestan.
History of use
Trade in turquoise crafts, such as this freeform pendant dating from
1000–1040, is believed to have brought the Ancestral Puebloans of
Chaco Canyon great wealth.
Moche turquoise nose ornament.
Larco Museum Collection, Lima, Peru
Backswords, inlaid with turquoise. Russia, 17th century.
Turquoise mosaic mask of Xiuhtecuhtli, the
Aztec god of fire.
The iconic gold burial mask of Tutankhamun, inlaid with turquoise,
lapis lazuli, carnelian and coloured glass.
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 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,[citation
needed] 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
Cabochons of imported turquoise, along with coral, was (and still is)
used extensively in the silver and gold jewellery of
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 structure created by an artificial
glazed ceramic product known as faience.
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 around 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 many cultures of the Old and New Worlds, this gemstone has been
esteemed for thousands of years as a holy stone, a bringer of good
fortune or a talisman. The oldest evidence for this claim was found in
Ancient Egypt, where grave furnishings with turquoise inlay were
discovered, dating from approximately 3000 BCE. In the ancient
Persian Empire, the sky-blue gemstones were earlier worn round the
neck or wrist as protection against unnatural death. If they changed
colour, the wearer was thought to have reason to fear the approach of
doom. Meanwhile, it has been discovered that the turquoise certainly
can change colour, but that this is not necessarily a sign of
impending danger. The change can be caused by the light, or by a
chemical reaction brought about by cosmetics, dust or the acidity of
Hathor was associated with turquoise, as she was the
patroness of Serabit el-Khadim, where it was mined. Her titles
included "Lady of Turquoise", "Mistress of Turquoise", and "Lady of
In Western culture, turquoise is also the traditional birthstone for
those born in the month of December. The turquoise is also a stone in
the Jewish High Priest's breastplate, described in Exodus 28. The
stone is also considered sacred to the indigenous peoples of the
Southwestern United States Zuni and
Pueblo peoples of the American
Southwest, The pre-Columbian
Aztec and Maya also considered it to
be a valuable and culturally important stone.
Some natural blue to blue-green materials, such as this botryoidal
chrysocolla with drusy quartz, are occasionally confused with, or used
to imitate turquoise.
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
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
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 and
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 gemologists 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 pungent 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
An early turquoise mine in the Madan village of Khorasan, Iran
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. Gemologists can detect these treatments using a
variety of testing methods, some of which are destructive such as the
use of a heated probe applied to an inconspicuous spot will reveal
oil, wax or plastic treatment.
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.)
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 (sodium silicate) 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
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.
The use of
Prussian blue and other dyes (often in conjunction with
bonding treatments) to "enhance” its appearance, make uniform or
completely change the 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.
Perhaps the most extreme of treatments is "reconstitution", wherein
fragments of fine turquoise material, too small to be used
individually, are powdered and then bonded with resin to form a solid
mass. Very often the material sold as "reconstituted" turquoise is
artificial, with little or no natural stone, made entirely from resins
and dyes. In the trade "reconstituted" turquoise is often called
"block" turquoise or simply "block."
Since finer turquoise is often found as thin seams, it may be glued to
a base of stronger foreign material for reinforcement. These stones
are termed "backed," and it is standard practice that all thinly cut
turquoise in the
Southwestern United States
Southwestern United States is backed. Native
indigenous peoples of this region, because of their considerable use
and wearing of turquoise, have found that backing increases the
durability of thinly cut slabs and cabochons of turquoise. They
observe that if the stone is not backed it will often crack. Early
backing materials included the casings of old model T batteries, old
phonograph records, and more recently epoxy steel resins. Backing of
turquoise is not widely known outside of the Native American and
Southwestern United States
Southwestern United States jewellery trade. Backing does not diminish
the value of high quality turquoise, and indeed the process is
expected for most thinly cut American commercial gemstones.[citation
Valuation and care
Slab of turquoise in matrix showing a large variety of different
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 egg blue (in reference to the eggs of the American
robin). Whatever the colour, for many applications, turquoise
should not be 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
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
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 jewellery 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 buildup 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
Gemology and Jewelry portal
List of minerals
^ Hurlbut, Cornelius S.; Klein, Cornelis (1985). Manual of Mineralogy
(20th ed.). New York, NY: John Wiley and Sons.
^ a b c "Turquoise: mineral information and data". mindat.org.
^ a b c d e Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.;
Nichols, Monte C., eds. (2000). "Turquoise". Handbook of Mineralogy
(PDF). IV. Chantilly, VA: Mineralogical Society of America.
^ a b Palache, C.; Berman, H.; Frondel, C. (1951). Dana's System of
Mineralogy. II (7th ed.). Wiley. pp. 946–951.
^ a b c d Turquoise. minerals.usgs.gov
Turquoise R050554". RRUFF™ Project.
^ Minerals of Nevada.
Special Publication 31.
Nevada Bureau of Mines.
pp. 78–81, 443–445.
^ Kostov, R. I., J. Chapman, B. Gaydarska, I. Petrov, A. Raduntcheva.
Turquoise – archaeomineralogical evidences from the Orlovo
prehistoric site (Haskovo district, Southern Bulgaria). – Geology
Mineral Resources, 14, 7-8, 17-22.
^ a b Watson, Martin. "
Turquoise – The
Gemstone of Tibet". Archived
from the original on March 19, 2007. Retrieved 2007-06-01.
China Exhibition". Washington, D.C.: National Gallery of Art. 1999.
^ Shepardson, Mathew. "Does
Turquoise Change Color?". T. Skies.
Retrieved 11 March 2018.
^ Bulletin of the Egyptian Museum 2007, By The Supreme Council of
Turquoise By Joe Dan Lowry, p.36-41
^ Collector's Guide Volume 17, sharing the art of New Mexico. 2003, p.
Turquoise By Joe Dan Lowry, p.34
^ a b Harriss, Joseph A. "Tantalizing Turquoise". Archived from the
original on 2008-02-01. Retrieved 2007-06-01.
British Museum (2000).
Aztec turquoise mosaics. Retrieved November 15,
2004 from www.thebritishmuseum.ac.uk
Dietrich, R. V. (2004). Turquoise. Retrieved November 20, 2004 from
Turquoise Mine 
King, R. J. (2002). "Turquoise". Geology Today. 18 (3): 110–114.
Pogue, J. E. (1915). The turquoise: a study of its history,
mineralogy, geology, ethnology, archaeology, mythology, folklore, and
technology. National Academy of Sciences, The Rio Grande Press,
Glorieta, New Mexico. ISBN 0-87380-056-7
Schadt, H. (1996). Goldsmith's art: 5000 years of jewelry and
Art Publisher, Stuttgart, New York.
Schumann, W. (2000). Gemstones of the world, revised edition. Sterling
Publishing. ISBN 0-8069-9461-4
Webster, R. (2000). Gems: Their sources, descriptions and
identification (5th ed.), pp. 254–263. Butterworth-Heinemann,
Great Britain. ISBN 0-7506-1674-1
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