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Turquoise

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Formula:
Cu(Al,Fe3+)6(PO4)4(OH)8 · 4H2O
System:
Triclinic
Colour:
bright blue, sky-blue, ...
Hardness:
5 - 6
Member of:
Name:
Named from French "turques" or "turquois" meaning "Turkish" the original material found on the south slopes of the Al-Mirsah-Kuh Mountains (Iran), but which found its way to Europe via Turkey. The name was known at least as early as the 17th century C.E. Turquoise and members of its group were redefined by Foord and Taggert in 1998, with turquoise reserved for an end-member composition. Foord and Taggert (1998) also noted that most of the gem material labeled "turquoise" is inhomogeneous and that planerite is the most common constituent in commercial "turquoise".
Isostructural with:
Turquoise Group. Chalcosiderite-Turquoise Series. Planerite-Turquoise Series. The copper analogue of Faustite.

A secondary mineral occurring in the potassic alteration zone of hydrothermal porphyry copper deposits. Also formed by the action of meteoric waters, usually in arid regions, on aluminous igneous or sedimentary rocks (as vein filling in volcanic rocks and phosphatic sediments).

Visit gemdat.org for gemological information about Turquoise.

Classification of Turquoise

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
8.DD.15

8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
D : With only medium-sized cations, (OH, etc.):RO4= 2:1
Dana 7th ed.:
42.9.3.1
42.9.3.1

42 : HYDRATED PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
9 : (AB)7(XO4)4Zq·xH2O
19.2.8

19 : Phosphates
2 : Phosphates of Cu
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http://www.mindat.org/min-4060.html
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Occurrences of Turquoise

Geological Setting:
Secondary mineral in potassic alteration zone of porphry copper deposits. Vein fillings in volcanic rocks and phosphate-rich sediments.

Physical Properties of Turquoise

Sub-Vitreous, Resinous, Waxy, Dull, Earthy
Diaphaneity (Transparency):
Transparent, Translucent, Opaque
Comment:
Dull to waxy in massive varieties, subvitreous in crystals.
Colour:
bright blue, sky-blue, pale green, blue-green, turquoise-blue, apple-green, green-gray
Comment:
Ferric iron substitution may cause the color to be green
Streak:
Pale greenish blue to white
Hardness (Mohs):
5 - 6
Tenacity:
Brittle
Cleavage:
Perfect
on {001}, good on {010}
Fracture:
Irregular/Uneven, Sub-Conchoidal
Density:
2.6 - 2.8 g/cm3 (Measured)    2.91 g/cm3 (Calculated)

Crystallography of Turquoise

Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Cell Parameters:
a = 7.409(1) Å, b = 7.635(1) Å, c = 9.914(2) Å
α = 111.356°, β = 114.973°, γ = 69.532°
Ratio:
a:b:c = 0.97 : 1 : 1.298
Unit Cell Volume:
V 449.39 ų
Z:
1
Morphology:
Crystals rare. Steep pinacoidal crystals exhibiting {010}, {110} and {001}. Fine granular, globular crusts, veinlets, massive.

Crystallographic forms of Turquoise

Crystal Atlas:
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Turquoise no.1 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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Crystal Structure

Structure
Reference
Kolitsch U Giester G (2000) The crystal structure of faustite and its copper analogue turquoise Locality: Iron Monarch iron ore deposit, South Australia. Mineralogical Magazine 64:905-913.

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More Crystal Structures
Click here to view more crystal structures at the American Mineralogist Crystal Structure Database
X-Ray Powder Diffraction:
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Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction Data:
d-spacingIntensity
9.09 (50)
6.17 (70)
4.80 (60)
3.68 (100)
3.44 (70)
3.28 (70)
2.91 (80)
2.02 (60)
Comments:
ICDD 6-214; A very weak d(010) peak near d = 9.0 is indicative of A-site vacant material, such as planerite.

Optical Data of Turquoise

Type:
Biaxial (+)
RI values:
nα = 1.610 nβ = 1.615 nγ = 1.650
2V:
Measured: 40° , Calculated: 44°
Birefringence:
0.040
Max Birefringence:
δ = 0.040
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
r < v strong
Pleochroism:
Weak
Comments:
X= colorless
Z= pale blue or pale green

Chemical Properties of Turquoise

Formula:
Cu(Al,Fe3+)6(PO4)4(OH)8 · 4H2O
Essential elements:
All elements listed in formula:
Common Impurities:
Fe,Ca

Relationship of Turquoise to other Species

Series:
Forms a series with Chalcosiderite (see here)
Forms a series with Planerite (see here)
Member of:
Other Members of Group:
Aheylite(Fe2+,Zn)Al6(PO4)4(OH)8 · 4H2O
ChalcosideriteCu(Fe3+,Al)6(PO4)4(OH)8 · 4H2O
Faustite(Zn,Cu)Al6(PO4)4(OH)8 · 4H2O
PlaneriteAl6(PO4)2(HPO4)2(OH)8 · 4 H2O
8.DD.05ChenevixiteCu2Fe23+(AsO4)2(OH)4
8.DD.05LuetheiteCu2Al2(AsO4)2(OH)4
8.DD.10Akrochordite(Mn2+,Mg)5(AsO4)2(OH)4 · 4H2O
8.DD.10GuanacoiteCu2Mg3(AsO4)2(OH)4 · 4H2O
8.DD.15Aheylite(Fe2+,Zn)Al6(PO4)4(OH)8 · 4H2O
8.DD.15ChalcosideriteCu(Fe3+,Al)6(PO4)4(OH)8 · 4H2O
8.DD.15Faustite(Zn,Cu)Al6(PO4)4(OH)8 · 4H2O
8.DD.15PlaneriteAl6(PO4)2(HPO4)2(OH)8 · 4 H2O
8.DD.15AfmiteAl3(OH)4(H2O)3(PO4)(PO3OH) · H2O
8.DD.20Childrenite(Fe2+,Mn2+)Al(PO4)(OH)2 · H2O
8.DD.20Eosphorite(Mn2+,Fe2+)Al(PO4)(OH)2 · H2O
8.DD.20Ernstite(Mn2+,Fe3+)Al(PO4)(OH,O)2 · H2O
19.2.1LibetheniteCu2(PO4)(OH)
19.2.2CornetiteCu3(PO4)(OH)3
19.2.3ReichenbachiteCu5(PO4)2(OH)4
19.2.4LudjibaiteCu5(PO4)2(OH)4
19.2.5PseudomalachiteCu5(PO4)2(OH)4
19.2.6NissoniteCu2Mg2(PO4)2(OH)2 · 5H2O
19.2.7ZapataliteCu3Al4(PO4)3(OH)9 · 4H2O
19.2.9SieleckiiteCu3Al4(PO4)2(OH)12 · 2H2O
19.2.10PlaneriteAl6(PO4)2(HPO4)2(OH)8 · 4 H2O
19.2.11HentscheliteCuFe23+(PO4)2(OH)2
19.2.13ChalcosideriteCu(Fe3+,Al)6(PO4)4(OH)8 · 4H2O
19.2.14PhosphofibriteK<0.5(Fe3+,Cu)8(PO4)6(OH)7 · 7H2O

Other Names for Turquoise

Other Information

Not fluorescent in UV
Other Information:
Soluble with difficulty in HCl.

Often found as pseudomorphs after orthoclase; also after apatite, bone and teeth.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Industrial Uses:
Jewelry stone.

References for Turquoise

Reference List:
Tavernier (1678) Voy. en Turquie, en Persie, etc., Paris.

Bocconi (1697) Museo di Fisica, etc.: 278 (as Turchine).

Fischer (1806) Mem. Soc. nat. Moscou: 1 (as Turquois orientale).

John (1806) Mem. soc. nat. Moscou: 1 (as Johnite).

John (1807) Journal für Chemie und Physik, Nuremberg: 3: 93 (as Johnite).

Onomasticon Min. Mus. Imp. Moscou (1811) (as Calaite).

Hausmann, J.F.L. (1813) Handbuch der Mineralogie 3 volumes, Göttingen: 444 (as Hydrargillite).

Blake (1883) American Journal of Science: 25: 197 (as Chalchuite).

Dana, E.S. (1892) System of Mineralogy, 6th. Edition, New York: 844.

Carnot (1894) Comptes rendus de l’Académie des sciences de Paris: 118: 995.

Penfield (1900) American Journal of Science: 10: 346.

Schaller (1912) American Journal of Science: 33: 35.

Schaller (1912) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 50: 120.

Pogue, J.E. (1915) The Turquois, a study of its history, mineralogy, geology, ethnology, archaeology, mythology, folklore, and technology. National Academy of Science Mem. 12, part 2, 207 pp.

Davy (1929) Transactions of the Royal Geology Society of Cornwall: 16: 43.

Hintze, Carl (1931) Handbuch der Mineralogie. Berlin and Leipzig. 6 volumes: 1 [3B]: 941.

Ball (1941) Bulletin of the Bureau of American Ethnology, Smithsonian Institution, no. 128 (Uses of turquoise in N. & S. America).

Pearl (1941) Economic Geology: 36: 335.

Northrop (1942) University of New Mexico Bulletin no. 379: 313.

Pearl (1945) Gemmologist, London: 14: 62.

Graham, R. (1947) X-ray study of chalcosiderite and turquoise. University of Toronto Studies, Geology Series, 52, 39–53.

Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124 pp.: 646.

American Mineralogist (1953): 38: 964.

Cid-Dressner, H. (1965) Determination and refinement of the crystal structure of turquois, CuAl6(PO4)4(OH)8 •4H2O. Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 121: 87–113.

Zeitschrift für Kristallographie: 121: 87-113.

Guthrie, G.D., Jr. and D.L. Bish (1991) Refinement of the turquoise structure and determination of the hydrogen positions. Geological Society of America, Annual Meeting Abstracts with Program, 23(5), 158A (abs.).

Foord, E.E. & Taggart, J.E. (1998): A reexamination of the turquoise group; the mineral aheylite, planerite (redefined), turquoise and coeruleolactite. Mineralogical Magazine, 62, 93-111.

Extra Lapis No. 16 (1999).

Anthony, J.W., Bideaux, R.A., Bladh, K.W., and Nichols, M.C. (2000) Handbook of Mineralogy, Volume IV. Arsenates, Phosphates, Vanadates. Mineral Data Publishing, Tucson, AZ, 680pp.: 606.

Kolitsch, U. and G. Giester (2000): The crystal structure of faustite and its copper analogue turquoise. Mineral. Mag. 64, 905-913.

Y. A. Abdu, S. K. Hull, M. Fayek & F. C. Hawthorne (2011): The turquoise-chalcosiderite Cu(Al,Fe3+)6(PO4)4(OH)8•4H2O solid-solution series: A Mössbauer spectroscopy, XRD, EMPA, and FTIR study. American Mineralogist 96, 1433-1442.


http://www.turquoiseguide.com/index.htm

Internet Links for Turquoise

Specimens:
The following Turquoise specimens are currently listed for sale on minfind.com.

Localities for Turquoise

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
Mineral and/or Locality  
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