TURQUOISE

( Fr- turquoise; Ger- Türkis/Türkisblau; Nor- turkis; Rus )

TURQUOISE, CuAl6(PO4)4(OH)8·4H2O.

A. Turquoise mass (height - 6.6 cm) from Gabbs, Nye County, Nevada. Canadian Museum of Nature. (© photo by Jeffrey A. Scovil)

B. Turquoise. Polished pieces (top right,  width - ca. 2 cm). Shades of the Earth. (© photo by Jeffrey A. Scovil)

C. Turquoise.  Traditional squash blossom necklace (pendant portion, height - 7.5 cm;  length of necklace -- 2/3rds of which has been cropped as shown here  - 75 cm).  Navajo handmade.   (© photo Cowboy and Lady,  www.cowboyandlady.com)

D. Turquoise. Carved eagles (width - 21.5 cm). Betty Llewellyn collection. (© photo by Jeffrey A. Scovil)

DESCRIPTION: Compact, massive variety of turquoise (see REMARKS):
    Colors - sky blue to deep bluish green, yellowish, gray -- Pogue (1915) describes the color as ranging "from a beautiful sky-blue to an unsightly pale green ... [with] a diversity of intermediate shades."   Choudhary (2010) records and presents colored photographs of marketed turquoise and turquoise matrix with several different colors -- e.g., blue, purple to purple-pink and yellow-green;  all of them are turquoise bonded with a colored polymer.  He also notes, for example, how each reacts to solvents such as acetone and methylene chloride.
    H. 5-6;  
"Elgen" (="Eljen") treated turquoise -- the treatment using an undisclosed proprietary treatment used to bind and stabilize turquoise -- has a hardness of 7 (Weldon, 2007) 
    S.G. 2.6-3.2
    Light transmission - opaque
    Luster - mattelike to waxy
    Breakage - subconchoidal fracture
    Miscellany - typically occurs as micro- to cryptocrystalline reniform masses; decrepitates -- i.e., explodes into fragments -- when heated.

    Also - Turquoise with an anastomosing yellowish brown or gray to nearly black matrix is frequently called Turquoise matrix.  The matrices commonly consist largely of limonite and/or sandstone but other mineral and rock constituents have also been found to occur. 

    And - A massive, greenish, zinc-rich member of the turquoise group, faustite -- e.g., that from Neyschabour, Iran -- has also been used as a gemrock.  It a hardness of ~ 4.5 and a specific gravity of ~ 2.9.

OTHER NAMES: Gubelin (1966) gives a summary of terms used for this gemrock before the French called it turquoise  -- see, in particular, his list of the terms currently applied in Arabic, Armenian, Farsi and Russian.  Pearl (1976) lists more than forty "names for turquoise," several of which are not included in the following list. Those listed are ones I have found to be used fairly frequently and/or rather widely in today's marketplace and/or in current literature.

OCCURRENCES: Turquoise may be deposited in more than one way.  Most known turquoise, however, appears to have been formed as a secondary mineral under the influence of surface or near surface waters, typically in arid regions.  It commonly occurs as nodules or in veins, seams, lenses or crusts in brecciated zones within alumino-siliceous igneous or metasedimentary rocks.  Shigley et al. (2000) have tabulated localities and pertinent references for localities from which turquoise was recovered during the 1990s.

NOTEWORTHY LOCALITIES: The famous Shaded Cave of Nishâpur (Neyshabur), northwest of Maden, Khorassan Province, Iran (formerly Persia), which, by the way, is the birth place of Omar Khayam;  Wadi Maghara near the western edge of the Sinai Peninsula, Egypt;  at the copper deposits, Chuquicamata, Chile;  at the Cerillos mines, Turquoise Mt. (Mt. Chalchihuitl), Santa Fe County, New Mexico;  and at several places in New Mexico,  Arizona, Colorado and Nevada. Some of the southwestern United States turquoise has been recovered as a by-product of copper mining -- e.g., from the Santa Rita copper mine near Silver City, Grant County, New Mexico.  Attention is also directed to Chen et al. (2012) who give information about and illustrations of  turquoise from Zhushan County, Hubei Province, China;  references they cite give information about other deposits in central China (e.g., in Yun County).

USES: Turquoise may have been the first gemrock to be used in jewelry:  It is well documented that Egyptian Queen Zur (or Zer), wife of the second ruler of the first dynasty (~ 6000 (7500?) B.C.), wore bracelets made of gold and turquoise.  Gubelin (1966) provides a  short summary of this and other early uses of turquoise as a gemrock.  

Cabochons, both round and oval, and flat pieces as parts of several diverse pieces of jewelry, carvings (including Zuni fetishes),  and several other pieces such as the relatively large vase illustrated by Branson (1975) are examples. Silver-turquoise jewelry of the southwestern United States of America has gained worldwide recognition.  And, turquoise has been used alone or as parts of mosaics, inlays or overlays that adorn surfaces of several diverse articles fashioned from clay (pottery), leather, fabrics and even other gemrocks;  one especially interesting example is a faceted rock crystal (quartz) backed by a slice of turquoise (Choudhary, 2013). 

REMARKS:  Turquoise is from Old French meaning Turkish.  Gubelin (1966), writes the following about the early application and resultant origin of the term: "This misnomer is readily explained by the fact that the first stones did not reach Europe directly from Persia [i.e., Iran], but rather through the intercession of seafaring Venetians who purchased them at Turkish bazaars."  

 It is virtually axiomatic that turquoise must be treated if it is to be used in jewelry that is likely to come into contact with perspiration, hair sprays, perfume, etc. Otherwise, it will – over time – become stained and/or have its depth of color reduced and lose its appeal;  This is true because of its relatively high porosity.  According to Indian legend, such treatments date back to ancient times when animal fat was used as a coating (Anonymous, 1949);  one example for which only so-to-speak hearsay documentation is recorded is: "Dr. Ralph Holmes of Columbia University reported reading in a 13th Century Persian work the fact that applications of Yak butter would improve the color of poor turquois." (Crowningshield,1958-59) 

Today, treatments of "normal" turquoise include dyeing;  waxing or oiling; and  impregnation with such things as paraffin (wax), shellac, varnish,  lacquer, epoxy resin, a plastic or even "water glass," and Crowningshield (1962) has described a few beads that  were painted before being coated with clear lacquer. In fact, combinations of  two or more  processes are frequently involved;  an apparently especially common one is using a colored impregnating material to improve the color as well as reduce the porosity of the original turquoise.  Also, much turquoise in the marketplace has been so-to-speak stabilized (i.e., hardened) by inorganic mineral salts such as colloidal silica and sodium silicate (water glass).  Fortunately -- or, depending on one's viewpoint, perhaps unfortunately -- most treated turquoise can be recognized or determined to be such relatively easily -- e.g., waxing can be detected because waxed turquoise will "sweat" when touched with hot point -- see Figure 7, p.189, volume 34 of Gems & Gemology.  Indeed, stabilization frequently darkens and saturates the color -- not at all bad from an aesthetic standpoint -- as well as serving to make the turquoise more durable.

Two exceptions seem noteworthy: 1. the "Zachery-treated turquoise," which is virtually impossible to distinguish from some high quality, naturally dense turquoise except by chemical analyses.
Although details about  this proprietary procedure have not been published, Fritsch et al. (1999), provide some insightful statements, which they received from James E. Zachery, the "entrepreneurial electrical engineer who 'grew up' in the turquoise trade" and devised the treatment.  Two aspects are of particular interest: 1.only natural turquoise precursors that are of at least medium quality can be so treated;  and  2."Zachery-treated turquoise" contains more potassium than its untreated precursors.  In any case, the increased durability of this product renders it more easily and safely worked and polished, and its reduced porosity means it will not absorb fluids such as perspiration and fluid-based cosmetics, which, as just mentioned, frequently cause untreated turquoise to lose its depth of color and/or take on less than attractive unnatural colors.  2. See note re "Elgen" treated turquoise in DESCRIPTION, under H. (hardness).   [*+*A more recently used proprietary process, designated Eljen ..., is treated by Owens and y Eaton-Magaña (2009).]

Some turquoise matrix has been dyed selectively so its matrix takes on a darker color and thus becomes more distinct.  Also, some fashioned pieces -- e.g., carvings -- made of turquoise, especially that of poor quality, have been selectively dyed black to make them resemble natural turquoise matrix.

So far as turquoise related legends, one that especially intrigues me relates to "old Germany."  The tale I heard holds that turquoise was commonly used for engagement rings, and that it was thought to retain its preferred color only so long as love endured;  that if it  faded or turned to another color the one wearing it was being unfaithful.  One has to wonder:  Did some poor quality turquoise take on the role of being a so-to-speak false witness that led to the breaking up of families? 

In the pre-Columbian western hemisphere, Aztecs, Incas, Mayas, and their predecessors worshiped and wore turquoise in religious ceremonies as well as for ornamentation.  These uses and stories relating to them notwithstanding, one of my favorite turquoise-related legends comes from, I believe, the Zunis of North America:  It holds that the blue coloring of the sky represents light from their "spirit bird" reflected from the top of a mountain of turquoise. However, in an opposite sense other Native Americans of  the southwestern United States region are said to have thought  turquoise so-to-speak stole its color from the sky.   More recently, Karl Glazebrook and Ivan Baldry, two Johns Hopkins University astronomers, after "mooshing for fun . . . [through] data [derived] from a serious study of more than 200,000 galaxies . . . revealed to the American Astronomical Society . . . [that the color of the cosmos is] pale turquoise" (Comarow, 2002).  [[Subsequently, however, Glazebrook and Baldry (April 4, 2002) reported  that their initial turquoise-colored determination was based on an error in calculation, and the color really is a light off-white, for which they favored the designation "'Cosmic Latte' [because of their] being caffeine biased!"  (www.pha.jhu.edu/~kgb/cosspec/).  --  If one were a believer in spirits et al., (s)he might wonder if their earlier miscalculations and announcement were predestined forethought, eh??!.

A most interesting recovery procedure was employed at the Los Cerrillos turquoise mines near Santa Fe, New Mexico, which were apparently worked long before Europeans came to America:  Fires were built atop, within fractures or beneath ledges of the turquoise outcrops, and water was poured on the hot surfaces thereby setting up thermal stresses that broke the rock into pieces small enough for easy removal and transport.

Turquoise is the state gem of New Mexico; the state semiprecious gemstone of Nevada;  and the state gemstone of Arizona, where prior to its gaining this status, the  ''official neck-wear" of the state was the bola tie and the silver bola tie adorned with turquoise is generally considered as the the official 'Bola Tie.'(Arizona 1977 Road Map, published by Arizona Department of Transportation).  Turquoise also is said to be the national gemstone of Iran ; and, according to Arem (1987) "the national gem of ... [Tibet, where] green is the most prized color."  [It seems prudent to note that to date I have been unable to document these last two attributions.] Also, in 1948, turquoise was adopted by directors of the South African Jewelers Association, Ltd. as the official birthstone for December. 

SIMULANTS:  "Turquois ... was one of the earliest, if not the earliest, gemstones to be imitated. ... [e.g.,] several turquois-colored objects found during archaelogical excavations in Egypt ... consisted of frit composed of crystalline compound[s] of silica (quartz pebbles), copper (malachite, for example) and calcium (natron, for example)... [And,] objects of glass colored turquois-blue with copper compounds, have been discovered at Thebes, and glass pieces colored by cobalt were found in the tomb of Tut-Ankhamen (Tutenkhamon)." (Webster, 1957-58, p.115).  

Several "names that suggest but are not turquoise" that are listed by Pearl (1976) are not included on the following list because I have been unable to find information about them;  many of the excluded materials are referred to by binomial terms with turquoise preceded by the adjectives such as Australian, Californian, fossil, ivory and  tooth; include the terms burnite, copper-minerals rock, dyed mineral mixture or neolith; or are of the "neo-turquoise" and "turquoise de nouvelle roche" genre.  In any case, I suspect at least some of those designations are synonyms for terms that are on the following list -- e.g., Pearl's fossil and tooth turquoise and perhaps even his ivory turquoise may be the same as bone turquoise (odontolite) and his copper-minerals rock may be the same as azurlite.

A rather special aspect of the simulation of turquois relates to turquois matrix:  An example is one that consists of turquois, plastic and metal flakes .  The metal flakes, at least most of which are in the matrix , described as "veining," were found to be copper.  (see Renfro and Owens, 2010)

A noteworthy amount of "Turquoise" in today's marketplace has been treated (See REMARKS)  or is reconstructed (see on this list).  If one wants to be sure that something is natural turquoise -- i.e., untreated -- (s)he should buy only from jewelers (et al.) who are completely trustworthy;  alternatively, (s)he may have any piece in question studied by an expert who has access to the relatively sophisticated equipment necessary to make such determinations.   However, a  few "rules of thumb" seem noteworthy:  "Untreated turquoise tends to be more porous than treated material and can often be brittle.  [and]  Natural turquoise is often 'backed'  with a rigid layer to ensure durability." (Weldon, 2007b)

***Aluminum phosphates colored blue by copper oleate have been compressed to form a material resembling turquoise. - [may require non-macroscopic means].

Amazon stone - green microcline feldspar. - [doesn't really look like turquoise and has two good cleavages].

***Assembled pieces of turquoise and also of restructured turquoise (q.v.) plus an adhesive (e.g.,  a dark brown plastic or epoxy) have been marketed as matrix (e.g., "spider web") turquoise. - [Appearance may suffice, but some pieces may require non-macroscopic means.].  Choudhary (2013) illustrates and describes a turquoise-rock crystal composite (bottom thin slice-relatively thick top, respectively) that is fashioned into a cabochon, of which it is said "the reason for it creation is still unclear."

Azurlite (azurchalcedony, chrysocolla chalcedony) - name sometimes given to blue or greenish blue chalcedony, the color of which is due to disseminated chrysocolla.  Some of this chalcedony, which has been recovered from copper deposits in Arizona and central Mexico, has an attractive light blue color that may resemble high quality turquoise. It has also been termed gumdrop blue (Koivula, Kammerling and Fritsch, 1994, p.49) - See also CHALCEDONY and  "CHRYSOCOLLA" entries. So far as I have been able to determine, this material has not yet been represented as turquoise. - [greater hardness (H. ~ 7) ].

Bayerite ("byproduct of the clay and aluminum industries ... [that is] chemically the same as gibbsite ... Al2O3·3H2O" ) plus a copper phosphate with a "'matrix' ... probably due to some amorphous iron coumpound" (Webster, 1957-58) -- noted as a "new imitation turquois from Germany," which simulates turquoise matrix. - [inferior hardness; "unnatural-looking" matrix].

Beryl and quartz rock, heat treated and dyed - [Dye concentrations apparently occur in fractures (Koivula, Kammerling and Fritsch, 1992, p.135)].

Bonded turquoise - See Assembled pieces and Restructured turquoise.

Bone turquoise (also called Odontolite (q.v.) and sometimes marketed as, for example, French or  occidental turquoise) - fossil bones, teeth or tusks of fossil animals, such as mammoths, that are either naturally or artificially stained blue or greenish blue by hydrous phosphates of iron (in some places recorded as the mineral vivianite) and/or copper. This material, used for the most part in the past, was recorded by Theophrastus (circa 315 B.C) in what is generally recognized as the oldest known treatise about minerals and rocks. - [Most bone turquoise can be seen to have retained its original organic structures.].  See also Ivory and Teeth entries in ZooGems folder, especially the third paragraph under REMARKS in the IVORY entry for some additional information about odontolite.  

Calcite plus a plastic binder, dyed blue - [Calcite effervesces with dilute HCl; plastic gives off characteristic odor when heated -- e.g., touched with a hot needle.].

Chalcedony containing disseminated particles of chrysocolla - see Azurlite.

Chalcedony of light color, stained or dyed blue - [superior hardness (H. ~ 7)].

Chinaware, appropriately colored and commonly glazed - [does not look like turquoise, especially when viewed with a handlens.].

Chinese turquoise (a mixture of steatite, calcite and quartz that has been dyed blue) - [The hardnesses of steatite and calcite are less than that of turquoise and the calcite component effervesces with cold dilute HCl.].

Chrysocolla - sintered chrysocolla has been suggested as a simulant -- I have not been able to document such use. - [inferior hardness (H. 1½ -2½)].

Chrysocolla quartz - blue to greenish blue chalcedony from copper deposits of Arizona and central Mexico, most of which is chalcedony with disseminated chrysocolla. - [superior hardness].

Clay, dyed blue - [When breathed on, scratched surfaces have a clayey odor.].

Eilat stone - sometimes marketed as impure turquoise; see CHRYSOCOLLA entry. - [Appearance should be sufficient.].

***Enamel - ceramic material appropriately colored (etc.) has been available since the early 1970s;  a necklace consisting of such enamel atop hollow gold spheres is recorded by Crowningshield (1966, p.46). - [Appearance suffices.].

***Faience - appropriately colored faience has been used for "turquoise" beads, etc., especially in the past. - [does not look like turquoise, especially when viewed with a handlens.].

Fossilized dentine - see Odontolite.

French turquoise - see Odontolite.

Gibbsite, dyed and in some cases plastic coated. - [inferior hardness (H. 2½ -3½)].

***Glass and frit  (usually opacified) - included here are the well-known Hubbell (sometimes spelled Hubble) beads (etc.), according to Lui (1995) "Named for Don Lorenzo Hubbell, a trading post operator in Arizona, the story suggests these were glass beads, made in Czechoslovakia to imitate fine Persian turquoise, and sold to Native Americans as a cheap substitute for the highly valued turquoise ... The name currently applies to any glass bead resembling turquoise or items thought to be Hubbell beads, regardless of where such were made ..."  Actually, that all-inclusive attribution is an overstatement: One glass that resembles turquoise, and has been carved and mounted in jewelry, has been marketed as "Japanese vintage turquoise glass."   More recently, specialty catalogs have described and illustrated jewelry  that includes turquoise-colored (and apparently also surficially patterned) glass that resembles turquoise. - [Small, Included bubbles are common;  luster, which if it can be seen, differs markedly -- check, for example, around the holes in beads.].

Hamburger turquoise - name given to an "imitation turquoise," the properties of which I have been unable to find descriptions.

Howlite, dyed blue -  According to the "Dictionary of gems and gemology ... " (GIA, 1974) "It [, itself,] is in demand for making bookends, spheres, ashtrays and similar ornamental and utilitarian articles. ... Outstanding localities are Nova Scotia and Tick Canyon, near Saugus, Los Angels Co., California." - [inferior hardness (H. 3½ - 4½)].

Imitation turquoise - name given to otherwise unidentified material in pictured in adverisements in some specialty house catalogs. - [I have not seen this material, so offer no criteria.].

Ivory, powdered, sintered and stained blue to resemble turquoise. - [Both hardness (H.~ 2½) and specific gravity (S.G. < 1.85) are less than those of turquoise].  See also Odontolite.

Jasper, dyed blue. - [superior hardness - see JASPER entry].

***Lacquer - i.e., turquoise -hued lacquer, which is produced, carved, etc. -- using virtually the same procedures described for cinnabar lacquer in the CINNABAR entry -- has been used to produce decorative items such as decorative carved snuff bottles. - [The fact that articles using this material are fashioned atop a background that do not resemble turquoise suffices to distinguish this material from turquoise.].

Lazulite - massive masses of this mineral. - [Typical color differs markedly  from typical colors of turquoise.].

Limestone and marble, stained blue, and in some cases plastic coated. - [inferior hardness; effervesces with dilute HCl; if coated, a hot point will melt the plastic.].

***Luroc (also Lauric) - one of the names given to so-called synthetic turquoise.  According to J.D. Luker (email received 09/06/01) , the son of J.P. Luker, who formulated the synthesis process, Luroc is "for all practical purposes identical to it [i.e., natural turquoise] in elemental analysis, hardenss (sic) and specific gravity. The only parameter that differs is that of X-ray diffraction."  And, he also noted that he is continuing his father's work and hopes, "as soon as is practicable ... to submit a sample [of the product of a significantly improved material] to an appropriate laboratory" to see if he now has a true synthetic turquoise. - [Scientific instruments would apparently be required.].

Magnesite -- i.e., porcelaneous secondary magnesite concretions -- dyed blue, etc. - [inferior hardness (H. 3½ - 4½) and greater specific gravity (S.G. 2.98-3.02)].

Marble, stained blue - see Limestone... listing.

***Mixtures - Recipes for two examples --one of which has been marketed as "Viennese turquois" -- are given by Webster (1957-58).  A more recently recorded example is the "Mixture of several materials, the main constituents being silicon dioxide and zinc oxide" (Fryer, 1983). - [Although appearance may suffice, see also the referenced articles.].

Nevada turquoise - see VARISCITE entry. This appellation is somewhat ambiguous in that Nevada turquoise without the quotation marks is a name frequently given to turquoise from Nevada.

Occidental turquoise - term sometimes applied to odontolite; see Bone turquoise. 

Odontolite - This name is a "catch-all" term for bone turquoise (q.v.).  It consists largely of the mineral widely referred to (at least in the older literature of mineralogy) as fluorapatite (~ Ca5(PO4)3F ).  Much of it that has been used to simulate turquoise is apparently fossilized mastodon ivory.  It has been marketed under such names as French turquoise, ivory turquoise and bone turquoise as well as turquoise with no so-to-speak disclaimer adjective.  Much of it has come from southwestern France, where it has been used since at least medieval times. The preceding statements are based largely on the article by Krzemnicki, Herzog and Zhou (2012), which also includes a rather extensive list of references.

***Plaster of Paris (appropriately colored) - [Texture as seen with naked eye or as seen through a handlens differs markedly from that of turquoise.].

***Plastic -diverse largely plastic mixtures -- e.g., with quartz and only minor turquoise -- have been used. -  [inferior hardness (H. 1-2)].

***Porcelain and frit- ceramic material appropriately colored (etc.) has been available since the early 1970s. - [Appearance suffices].

Prosopite - turquoise-blue prosopite from the State of Zacatecas, Mexico has been fashioned into items marketed as a turquoise substitute. - [inferior hardness (H. 4½)].

Quartzite, dyed blue - [superior hardness (H. 7)].

***Reconstructed ("molded" or "pressed") turquoise - sintered turquoise and/or chrysocolla and/or variscite OR, more commonly an acrylic plastic saturated with powdered turquoise, a dye, etc.  Four products that exemplify these materials are adco turquoise, neolith, syntho turquoise and turquite (cf. Vienna turquoise).  Although these materials are usually made into blocks and sawn for fashioning, at least some of  these materials have been molded directly into cabochons, etc. - [If differences are not readily apparent upon macroscopic examination (and they often are not), the fragmentary makeup of many of these materials is usually quite evident under the microscope.].

Sacred turquoise - blue smithsonite. - [See Smithsonite, below, and SMITHSONITE entry.].

Serpentine, dyed blue - [The typical hardness (H. ~ 3) is less than that of turquoise.].

Smithsonite (naturally blue) - [greater specific gravity (S.G. (4.3-4.5)].

***Soap - although not a simulant or meant to be one, it is interesting, I think, that among the soaps made and distributed by Rogue River Soaps & Supplies is “Turquoise in Nag Champa (the flavor),” which appears to closely resemble turquoise (See www.rogueriversoaps.com).

Soapstone (with a blue glaze applied) - according to Ogden (1982), prior to 3000 B.C., turquoise had a blue-glazed steatite as a rather common substitute. - [inferior hardness.].

***"Synthetic turquoise" - Pierre Gilson introduced a synthetic turquoise to the marketplace in the early 1970s.  It is often characterized as having a "cream of wheat" texture.  Another example is recorded only as from Russia (Koivula, Kammerling and Fritsch, 1994, p.57), and some Vienna turquoise (see below) has also been represented, apparently incorrectly, as synthetic turquoise. - [Any truly synthetic turquoise would very likely  have to be distinguished from natural turquoise by non-macroscopic means.].

"Turquoise occidentale" - see Vivianite. 

Utah turquoise - variscite from Utah - see VARISCITE entry.

Variscite - see VARISCITE entry.

***Vienna turquoise (Viennese turquoise) - a manufactured, essentially amorphous material, at least some of which may be a reconstructed turquoise. This material, which has the same general composition as turquoise, was once produced in Austria and a few other European countries and sold as a turquoise substitute. - [impossible to distinguish chemically from natural turquoise].

Vivianite (termed "turquoise occidentale," as distinct from "turquoise orientale" that is turquoise per se) - [an unlikely substitue!!; inferior hardness (H.1½ -2) ].

REFERENCES: Arem, 1992; Brown, 1983; Pearl, 1976; Pogue, 1915.

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