Mineralogical Magazine, February 1998, Vol. 62(1), pp. 93-111

A reexamination of the turquoise group: the mineral aheylite, planerite (redefined), turquoise and coeruleolactite

EUGENE E. FOORD M.S. 905, U.S. Geological Survey, Box 25046 Denver Federal Center, Denver, CO 80225, USA

AND

JOSEPH E. TAGGART, JR. M.S. 973, U.S. Geological Survey, Box 25046 Denver Federal Center, Denver, CO 80225, USA

The turquoise group has the general formula: Ao_IB6(PO4)4_x(PO3OH)x(OH)8"4H20, where x = 0-2, and consists of six members: planerite, turquoise, faustite, aheylite, chalcosiderite and an unnamed Fe>-Fe 3+ analogue. The existence of 'coeruleolactite' is doubtful. Planerite is revalidated as a species and is characterized by a dominant A-site vacancy. Aheylite is established as a new member of the group, and is characterized by having Fe2+ dominant in the A-site. Chemical analyses of 15 pure samples of microcrystalline planerite, turquoise, and aheylite show that a maximum of two of the (PO4) groups are protonated (PO3OH) in planerite. Complete solid solution exists between planerite and turquoise. Other members of the group show variable A-site vacancy as well. Most samples of 'turquoise' are cation-deficient or are planerite. Direct determination of water indicates that there are 4 molecules of water. Planerite, ideally [TA16(PO4)2(PO3OH)2(OH)8.4H20, is white, pale blue or pale green, and occurs as mamillary, botryoidal crusts as much as several mm thick; may also be massive; microcrystalline, crystals typically 2-4 micrometres, luster chalky to earthy, H. 5, somewhat brittle, no cleavage observed, splintery fracture, Dm 2;68(2), Dc 2.71, not magnetic, not fluorescent, mean RI about 1.60. a 7.505(2), b 9.723(3), c 7.814(2) A, ct 111.43 ~ [3 115.56 ~ 7 68.69~ V 464.2(1) ~3, Z = 1. Aheylite, ideally Fe2+ AI6(PO4)4(OH)a.4H20, is pale blue or green, and occurs as isolated and aggregate clumps of hemispherical or spherical, radiating to interlocked masses of crystals that average 3 micrometres in maximum dimension; porcelaneous-subvitreous luster, moderate to brittle tenacity, no cleavage observed, hackly to splintery fracture, not magnetic, not fluorescent, biax. (+), mean RI is about 1.63, Dm 2.84(2), Dc 2.90. a 7.400(1), b 9.896(1), c 7.627(1) _A, e~ 110.87 ~ 13 115.00 ~ Y 69.96~ V 460.62(9) A 3, Z = 1.

KEYWORD'~" turquoise group, planerite, aheylite, 'coeruleolactite', X-ray diffraction data.

Introduction relatively recently (Cid-Dresner, 1964, 1965; Cid-Dresner and Villarroel, 1972; and Guthrie MINERALS of the turquoise group have been and Bish, 1991, for turquoise; Giuseppeti et al., known since antiquity and have been valued for 1989, for chalcosiderite; Foord and Taggart, 1986, their use as gems. Pogue (1915) summarized what for planerite and aheylite). This paper presents was known about turquoise in his monograph. new complete chemical analyses of 15 pure However, the structure and chemistry of members samples and summarizes the elemental site of the group (Table 1) were not clear until occupancies of the various sites for the members

1998 The Mineralogical Society E. E. FOORD AND J. E. TAGGART, JR.

TABLE 1. Members of the turquoise group: general-formula: Ao_IB6(PO4)4_x(PO3OH)x(OH)6.4H20 where x = 0-2

A-site B-site (PO4)4-x (PO3OH)x Mineral name

[] A1 2 2 Planerite Cu A1 4 0 Turquoise Zn A1 4 0 Faustite Fez+ A1 4 0 Aheylite Ca? A1 4 0 Coeruleolactite

[] Fe3+ 2 2 unknown as yet Cu Fe3+ 4 0 Chalcosiderite Zn Fe3+ 4 0 unknown as yet Fe2§ Fe3+ 4 0 (unnamed)* Ca? Fe3§ 4 0 unknown as yet

* First reported by M/icke (1981) from Hagendorf, but without supporting chemical and structural data. Miicke (personal communication (1983) provided the authors with full data for the mineral, as submitted to the CNMMN IMA. The mineral was approved, but the proposed name was not. of the turquoise group. It also presents results of about 1 wt.% low from that for theoretical an examination of two specimens of blue to blue- turquoise. It is unfortunate that a direct determina- green 'coeruleolactite' from the type locality. tion for water was not done. Turquoise and other members of the group do In the case of the 'cuprofaustite' described by not contain 5 molecules of water as has been Kunov et aL (1982), this mineral is clearly a shown by some authors to the present time, but cation-deficient (A-site deficient) faustite. The only 4 molecules. The crystal structure determina- turquoise from the Kelly Bank mine, Rockbridge tions (Cid-Dresdner, 1964, 1965; Giuseppeti, et Co., VA (Mitchell and Freeland, 1978; Barwood al., 1989; Guthrie and Bish, 1991) for turquoise and Zelazny, 1982) has been shown to be and chalcosiderite also indicate four molecules to planerite (this study). The mineral described by be present. As vacancy becomes dominant in the Ivanov (1979) is best described as a cation- A-site, then the amount of protonation, to a deficient aluminian chalcosiderite. Similarly, the maximum of two of the phosphate groups, turquoise described from Paikhoy, Russia increases. Charge balance is maintained by the (Belyaev and Ievlev, 1990) is best characterized development of (PO3OH) groups as the A-site as a Cu-Fe bearing planerite. The turquoises occupancy decreases. The two sites for H are what (microprobe analyses with no direct determina- principally caused the number of molecules of tion of water) described by Silaev et al. (1995) molecular water to previously be reported as 4 or from Paikhoy and other locations in the Ural 5. Some minor H20 for OH substitution may also Mountains are turquoise-planerite. occur. Alteration processes such as those described by Van Wambeke (1971) do not Analytical methods account for the A-site cation deficiency in turquoise group minerals. Cations (Cu,Zn,Fe,A1,P) were determined on A chemical, X-ray and Mrssbauer examination small, hand picked samples ranging from 4 to of a turquoise from Greece (Sklavounos et al., 12 mg using the ICP technique described in 1992) showed 9.09 wt.% CuO, 0.26 wt.% BaO, Lichte et al. (1983, 1987). Early in this work A1203 35.7, Fe203 1.27, As205 0.14, P205 34.00 samples were digested with KOH fusion at 500~ and 19.41 wt.% H20 (by difference). This is Later in this technique the digestion was clearly a high Cu-containing turquoise with improved and 1 mg of sample was digested per essentially no A-site vacancy. The 19.41 wt.% ml of high purity 6 N HC1 (prepared by gaseous ]420, assigned by difference, is substantially more transfer of HC1 from concentrated hydrochloric than the ideal amount of 17.72 wt.% H20. P205 is acid over to double distilled water) using small

94 THE TURQUOISE GROUP

volumetric tubes, a stirring hot plate at 80 ~ C, and the Bryn Mawr College collection (Rand a micro-magnetic stir bar. Collection #8520). We also obtained some HzO- was determined gravimetrically after turqoise (USNM # 97340) from the Bishop drying at 105~ for four days. After drying, the mine, Lynch Station, VA that had been studied sample was then analysed for water at 900~ by by Schaller (1912). Five samples of aheylite were Karl Fisher titration using the technique of provided by Mr Richard A. Kosnar, and one by Jackson et al. (1985, 1987) and the results were Mr Anthony Jones. Many attempts were made to then reported as H20 + find, for analysis, specimens of white and blue varieties of 'coeruleolactite' from the Rindsberg Samples examined mine, Katzenelnbogen (als0 spelled Katzenellenbogen), Hesse (formerly Nassau), Analyses for a total of 15 samples of planerite, Germany, but only two specimens (of the blue aheylite, and turquoise, many with their museum to blue-green variety) were able to be obtained catalogue numbers, ideal compositions for through the courtesy of Mr Forrest Cureton (one turquoise, planerite and oJaeylite, along with one specimen), and H.J. and I.A. Wilke (given to Mr unpublished analysis of p[anerite from Arkansas, David Garske who gave the second specimen to are given in Table 2. Every effort was made to Mr Forrest Cureton). obtain early specimens of 'type' planerite from the Gumeshevsk copper mine, Urals, Russia, so SEM-EDS studies that the mineral could be properly revalidated. True type samples were not preserved as such in A Cambridge Stereoscan 250 Mk-1 instrument the mid-19th century. One specimen of planerite with attached Tracor Northern EDS system was was obtained from The Natural History Museum, used for examination, chemical characterization, London (specimen no. BM 36020, acquired about and photomicrographs of all turquoise group 1864), along with one specimen (dated 1869) minerals examined. from Harvard University (specimen 62121, Most specimens of members of the turquoise Liebener collection). Two old specimens were group m'e microcrystalline and apppear as earthy, obtained from the USNM (nos. R5524 and fine-grained, variable density materials. However, R9710). Additional specimens of planerite were the specimens of aheylite and planerite examined obtained from Charles University (Prague) in this study along with some turquoise samples (12389), and (unnumbered) from the Mining are micro-crystalline to macrocrystalline. SEM Institute of Leningrad (Gorny Institute). photos (Figs 1-8) show the complex and Specimens of planerite were also obtained from excellent crystallinity of these minerals. It

FIGS 1 and 2. FIG. 1 (left). SEM photo of a sphere of aheylite crystals from Huanuni, Bolivia. FIG. 2 (right). SEM photo at intermediate power showing diamond-shaped crystals making up the sphere shown in Fig. 1.

95 E. E. FOORD AND J. E. TAGGART, JR.

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96 THE TURQUOISE GROUP

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97 E. E. FOORD AND J. E. TAGGART, JR.

FIos 3 and 4. Fie. 3 (left). SEM photo at high power showing individual crystals of aheylite shown in Figs 2 and 3. FIG. 4 (right). SEM photo of planerite crystals (R9710) from Gumeshevsk, Urals, Russia.

should be pointed out that many crystalline members of the turquoise group. Instrumentation samples of turquoise group members are chemi- used was a Perkin-Elmer TGA 300 system. cally zoned and this chemical zonation often M6ssbauer data were collected through the correlates with colour zonation of various courtesy of D.L. Williamson (Colo. School of samples. For example darker green zones Mines). TGA data for two planerites (R9710 and contain more iron, darker blue zones contain R5524) indicate three discrete weight loss events: more copper, and rarely other elements such as 1. 170-200~ (H20), 2. 280-300~ (OH) and 3. Cr, V, and Zn show up as well. 340~ (PO3OH) (Fig. 9). Turquoise from Lynch Station, VA (9% vacancy) shows only one weight loss event at 420~ (Fig. 10). Similar results for TGA and M6ssbauer data Lynch Station turquoise were obtained by Mr. TGA studies were done in the laboratory of C. Henry Barwood (Indiana Geological Survey). The Gene Whitney (USGS). Both his assistance and molecular water in fully or nearly completely A- that of Kenneth J. Esposito, enabled us to do this site filled turquoise is tightly bound and is important aspect of characterization of the released together with (OH). To check the

FIGS 5 and 6. FIG. 5 (left). SEM photo of Lynch Station, VA, turquoise crystals (USNM #97340). FI6. 6 (right). SEM photo of turquoise crystals from Itatiaiucu iron mine, Minas Gerais, Brazil.

98 THE TURQUOISE GROUP

FIGS 7 and 8. FIG. 7 (left). SEM photo of a sphere of planerite-turquoise ('coemleolactite') from General Trimble's mine, Chester Co. PA. FIG. 8 (right). SEM photo showing a close-up view of the planerite-turquoise shown in Fig 7.

accuracy of the TGA apparatus, reference samples X-ray diffraction studies of wavellite, paravauxite and vivianite were also analysed. The total weight loss for each mineral Automated X-ray powder diffractometer scans agreed well with the ideal total water content. were made using a Norelco-Philips diffractometer Wavellite loses molecular water at 225~ and with the following analytical conditions: 40 kV OH at 335~ paravauxite looses water at 150~ and 30 mA, 1/2~ and 1/2 inch/rain, scan and OH at 270~ vivianite loses most of its water speed. Scans were made from 4 ~ to 76 ~ 20 in both at 180~ directions using graphite-monochromatized M~Sssbauer spectroscopy (by D.L. Williamson, Cu-K~I radiation (X = 1.54059 A). Averages of CSM) study of four planerites (one from the peak positions and intensities were taken from the BMNH, dated 1864, and probably provided by two scans. Scans were made ofplanerite, aheylite Hermarm (1862a, b) himself) from Gumeshevsk and a planerite-turquoise. Quartz was used as an indicates that all of the iron present is ferric and internal standard for the Gumeshevsk planerite not ferrous as stated by Hermalm (1862a). The and the Huanuni aheylite. Annealed CaF2 was other three specimens analysed are: USNM used as an internal standard for the planerite- #R5524, D.P. Grigoryev (#15, table 2), and turquoise from General Trimble's mine. Cell- Charles Univ. #12389. One sample of aheylite dimensions for turquoise from Lynch Station, VA from Huanuni, Bolivia was determined to have a were determined using monochromatized Cu-K~I maximum Fe3+/Fe2+ ratio of 0.05 thus indicating radiation with a Haag-Guinier camera, and NBS that virtually all of the iron present is ferrous. 540a silicon as an internal standard. The X-ray A detailed EPR, M/Sssbauer, absorption and data are given in Table 3. The similarities can chemical study was done (Zang and Lin, 1984) for readily be seen between these three species, but a sequence of turquoise samples containing there are some significant intensity differences of varying amounts of iron. As is well known the certain reflections: e.g. d(010) at about 9.0 A.. In blue to green coloration in turquoise is due to the true planerite, the A-site is empty and there is no Cu/Fe ratio and the relative amounts of Fe2+ and d(010) diffraction line present. Turquoise on the Fe3+ present. Pure blue samples have little or no other hand, with a filled A-site, shows a well- Fe3+ present (e.g., Khorassani and Abedini, 1976). defined d(010) peak. The diffraction pattern for Coloration in turquoise was also addressed by planerite contains less than half of the number of Nikolskaya et al. (1976). An increase in the diffraction maxima observed for turquoise. Peak amount of Fe 3+ is particularly effective in intensities and observed reflections for planerite producing a green coloration. Aheylite contains are substantially different from those of turquoise. appreciable Fe2+ but is only very faintly coloured For example the 211 reflection is the most intense blue to blue green. maximum for planerite and is not observed in

99 E.E. FOORDANDJ. E. TAGGA~JR.

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I00 THE TURQUOISE GROUP

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102 THE TURQUOISEGROUP

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103 E. E. FOORD ANDJ. E.TAGGART,JR.

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turquoise. Another major difference is the 9.914(2), c 7.635(1) ,~, ~ 111.356 ~ 15 114.973 ~ Y presence of the 1 T1 reflection in planerite that is 69.532 ~ V 460.64(9) ~3, Z = 1. not observed for turquoise. Unit cell dimensions for members of the turquoise group are compared Planerite in Table 4. Chalcosiderite and the Fe2+-Fe 3§ analogue of turquoise both have similar volumes Planerite, first described in 1862 by Hermann of about 502 ~3 while all of the other members of (1862a, b), was approved by the IMA CNMMN the group have volumes of about 460 ~3. Unit- as a revalidated mineral in 1984 along with the cell dimensions for the turquoise from Greece new species aheylite. The ideal formula for the (Sklavounos et al., 1992) were: a 7.52, b 10.24, c mineral is [~IA16(POa)2(PO3OH)2(OH)s.4H20. 7.70 A, ~ 111.30 ~ 13 115.12 ~ Y 69.32 A. These The mineral generally appears as white to pale cell dimensions are slightly larger than reported blue or pale green, mamillary, botryoidal crusts for turquoise (ICDD 6-214). A turquoise (0.88 A as much as several mm thick on substrates site occupancy) from Altar, Chile had: a ranging from quartz to other Al-phosphate 7.4100(2), b 7.6356(2), c 9.9052(3)A, c~ minerals. It is microcrystalline with an indivi- 68.652(1) ~, I3 69.639(1) ~, Y 65.034(1) ~ V dual grain size of 2-3 micrometres and some- 460.50 A 3, Z = 1, Dealt = 2.91 (Guthrie and times larger (Fig. 4). The luster is chalky to Bish, 1991). These dimensions and cell volume earthy, fair transparency on thin fragments, no agree closely with our determined cell data for fluorescence in SW or LW UV light, H. = 5, Lynch Station, VA Rtrquoise, viz. a 7.409(1), b moderate to brittle, no cleavage observed,

104 THE TURQUOISE GROUP

TABLE 4. Unit-cell dimensions for members of the turquoise group utilizing data from this work as well as from the literature

Turquoise Faustite Fe2+-Fe3+ Turquoise- Chalcosiderite Planerite Aheylite member planerite a 7.410 A 7.44 -A 7.67 A 7.526 A 7.672 A 7.505 .A 7.400 b 7.636 9.89 10.25 9.946 10.199 9.723 9.896 c 9.905 7.67 7.87 7.779 7.885 7.814 7.627 68.65 ~ 110.72 ~ 112.3 ~ 112.42 ~ 67.52 ~ 111.43 ~ 110.87 ~ [3 69.64 115.65 115.7 116.56 69.17 115.56 115.00 y 65.03 69.65 69.3 68.54 64.88 68.69 69.96 V 460.5~3 463.0 ~3 502.4~3 467.8 ~3 502.21 ,~3 464.2 ~3 460.6 ~3 Z 1 1 1 1 1 1 1 Guthrie ICDD Miacke,1983 this paper ICDD this paper this paper and Bish (1991) 6-216 (pers,comm.) 37-446

Note: data for turquoise and chalcosiderite are shown using an all acute cell.

splintery fracture, Dm 2.68(5) and Dc 2.71(5). ppm, Y 20 ppm, Zn 3000 pppm. All other Not magnetic. Individual refractive indices were elements not detected at respective limits of not able to be determined because of small grain detection. 2. (white, Rand Coll. 8520): Fe size, but the mean RI is about 1.60(1). The unit- 0.15%, Mg 0.01%, Ca 0.015%, Ti 0.07%, Si 1.5 cell parameters determined from a least-squares %, A1 major, Na <0.01%, K <0.01%, P major, Mn refinement are: a 7.505(2), b 9.723(3), e 30 ppm, Ba 150 ppm, Cr 15 ppm, Cu 500 ppm, V 7.814(2) A, ct 111.43 ~ 13 115.56 ~ y 68.69 ~ V 15 ppm, Y 70 ppm, Zn 300 ppm, and Zr 70 ppm. 464.2(1) 3, Z = 1. Indexed X-ray powder All other elements not detected at respective diffraction data are given in Table 3. limits of detection. A sample of small green spherulites ofplanerite Planerite was described from Ponikla, Bohemia from Dug Hill, near Avant, Garland Co., Arkansas by Cech et aL (1961). Planerite has also been (Smith, 1985), collected in 1937 by W.T. Schaller described from Japan (Matsubara et al., 1987, was completely analysed by M.D. Foster in 1951. 1988). ICDD 42-1318 lists indexed powder This analysis has not been published in the diffraction data for a Cu-bearing (2.42 wt.%) literature previously, and is included (analysis planerite from Toyoda, Kochi City, Shikoku, but 21) in Table 2. It can be seen that this planerite these data are not as complete as the data has about two-thirds of the A site vacant. It presented here for virtually end-member planerite contains 0.2 wt.% each of CreO3 and V205, both from the type locality. elements of which are responsible for the characteristic green colour of Arkansas wavellite. Aheylite A sample (analysis no. 20, Table 2) of planerite from the Mauldin Mountain Quarry, Mt. Ida, Aheylite was approved as a new mineral, and Montgomery Co., Arkansas, is virtually end- member of the turquoise group, by the IMA member planerite as is one of the samples from CNMMN in 1984. The mineral occurs with Gumeshevsk (analysis no. 19, Table 2). variscite-type L, sphalerite, pyrite, quartz, vivia- Six-step emission spectrographic analysis (by nite, wavellite and cassiterite. The type locality is N.M. Conklin, U.S.G.S.) of two samples of the Miraflores mine, District of Huammi, Dept. of planerite from General Trimble's Mine, East Oruro, Bolivia. The variscite-type L, aheylite, and Whiteland Township, Chester Co., PA, yielded: sphalerite are very late in the paragenetic 1. (pale blue, Rand Coll. 8520): Fe 0.07%, Mg sequence and form botryoidal, microcrystalline 0.003%, Ca 0.005%, Ti 0.0015%, Si 0.03%, A1 masses on earlier formed minerals. Individual major, P major, Na <0.01%, K <0.01%, Mn 50 spheres of the aheylite may be as much as 1 mm ppm, Ba 1500 ppm, Cr 15 ppm, Cu 3%, V 15 or more across but the other two species are much

105 E. E. FOORD AND J. E.TAGGART, JR.

smaller. The three minerals are late hydrothermal other phosphate minerals, etc. We made every crystallization products. effort in this study to analyse only pure materials The aheylite occurs as isolated and aggregate and with a direct determination of the water clumps of hemispherical to spherical, radiating to content. By so doing, we are able to show interlocked very pale blue or blue-green felted definitively that turquoise group members have and matted aggregates of crystals which average 3 only 4 molecules of water and that additional microns in maximum dimension (see Figs 1-3). water is accounted for by protonation of a The mineral is very pale blue or blue green, white maximum of two of the four PO4 groups streak, porcelaneous-semivitreous luster, trans- forming (PO3OH) groups to form planerite. parent in thin flakes, not fluorescent, H. 5-5.5, Some H20 for (OH) substitution may also take moderate to brittle tenacity, no cleavage observed, place (Fig. 10). Excess amounts of water in hackly to splintery fracture, D m 2.84, Do 2.90. Not turquoise, chalcosiderite, and faustite, are due to magnetic. The mineral is biaxial positive, non- solid solution towards planerite, or additional pleochroic, but individual indices could not be impurity phases containing significant amounts of determined because of the exceedingly small water. Light blue or blue-green 'turquoise' from grain size, mean R.I. is about 1.63. many world-wide localities is actually planerite Chemical analyses for aheylite are given in rather than turquoise. Pure or nearly pure Table 2 (nos. 1-8). This mineral may be best turquoise is quite rare as well, and the mineral thought of as the ferroan analogue of turquoise from the Bishop mine, Lynch Station, Campbell and faustite (Erd et al., 1953). It should be noted Co., VA, is the best high-purity, well-crystallized, that the mineral is zincian and in some samples highly Cu-substituted turquoise (e.g. Schaller, Zn(atomic) ~ Fe(atomic). Some A-site vacancy is 1912) that we examined. A re-determination of also present. Only one sample has Fe2§ greatly in the density of the turquoise that was analysed by excess of Zn or vacancy. Emission-spectrographic Schaller (1912) was made using methylene iodide analysis revealed the following trace elements: diluted with acetone: Dobs = 2.86(1); Dc~lo = 2.91. Mg 0.001%, Ca 0.007%, Ti - none, Mn 7 ppm, Ba Some material from Lynch Station is intermediate 15 ppm, Be 15 ppm, Co 15 ppm, Cr 7 ppm, Cu 2 between turquoise and chalcosiderite, and a few ppm, Ni 7 ppm, Sn 20 ppm, V 200 ppm. samples of chalcosiderite were found as well in a Unit-cell dimensions, calculated from least- batch of assorted samples from the mine (J. Nelen squares refinement of powder diffraction data are: microprobe data, 1984, pers. comm.). a 7.400/~(1), b 9.897(1), c 7.627(1) A, ~ 110.87 ~ Thus, planerite is characterized as the member 13 115.00, y 69.96, V 460.62(9)~3, Z = 1. See of the turquoise group with the A-site predomi- Table 3 for indexed X-ray powder diffraction data nantly to completely vacant. A complete grada- for planerite, aheylite, and turquoise. tion (solid-solution) series exists between The mineral is named for Allen V. Heyl planerite and turquoise based on the number of (1918-) (U.S. Geological Survey, retired) in available analyses from this paper and from the particular recognition of his work on Mississippi- literature (e.g. Matsubara et al., 1987, 1988). Valley type ore deposits, as well as ore deposits in Much of the material described as turquoise in the general. literature is actually planerite. However, the name turquoise should be retained for gemological and Discussion historical uses. There appears to be significant solid-solution between chalcosiderite and Only relatively few bulk samples of members of turquoise based on available reliable analyses, the turquoise group are pure or nearly so. and there should be a complete solid solution Numerous references exist in the literature that series between faustite and turquoise, but the contain analyses of impure material. Recent such number of known faustite occurrences is quite papers include those of: Boriskin and Kuzmina small. Aheylite shows substitution with both (1976), Turesebekov et al., 1979; and Yakontova planerite and faustite components. et al. (1989). The most common impurity element Crystals of turquoise and other members of the is Si, although in some cases, small amounts of Si group for that matter, larger than about 0.1 mm may substitute for P. Impurities have been shown are rare. As noted by Braithwaite (1981), as of by other authors as well as by the present authors 1981 only the Bishop mine, Lynch Station, VA, to be many different things: amorphous silica, and Ottrr, near Vielsalm, Ardennes, Belgium quartz, kaolinite, montmorillonite, allophane, were known localities for well crystallized

106 THE TURQUOISE GROUP

fully vacant 21p ideal planerite 20 19 = 90 18 80 70 A-site 60 14 e occupancy .9 (percent) 50 lO 40 30 2O ,

10 1~ 12 fully occupied 11__ _ ideal turquo{s~-aheyljte 17 18 19 20 21 22

Weight percent H20 +

F/G. 10. Plot of wt.% H20 vs percentage occupancy of the A-site (going from ideal turquoise and aheylite to planerite). Solid dots represent analyses fi'om this work or ideal compositions of end-members. Open triangle represents analysis from Schaller (1912).

turquoise. Braithwaite added three British occur- Of all of the known members of the turquoise rences: Hensbalxow and Wheal Remfry china clay group, fanstite (from two localities: Nevada and pits, on St. Austell Moor, and Wheal Phoenix Neyschapur, Iran); the unnamed Fe>-Fe 3+ (Stowe's Mine), Linkinhome, all in Cornwall. member (one locality: Rotlgufschen, Waldgirmes, Turquoise crystals also occur at the Narooma Saxony, Germany) (Mticke, pel~. comm., 1983) mine, NSW, Australia (Braithwaite, 1981; Price, and aheylite (one locality: Bolivia), are the rarest. 1981). Well-crystallizedturquoise associated with A Zn-bearing (to 2.6 wt.% Zn) turquoise from quartz and dickite occurs at the Itatiancu iron Burkantau region (central Kyzylkum), Russia was mine, southwest ofBelo Horizonte, Minas Gerais, described by Boriskin (1974). Brazil (Fig. 6). Chalcosiderite, it should be noted, Varietal names such as cuprofaustite or is a rare mineral, known from only a few localities alumochalcosiderite (Ivanov, 1979; Kunov et al., including: Cole and Shattuck shafts, Bisbee, 1982, 1986) should not be used, rather they would Cochise Co., AZ; Wheal Phoenix, Linkinhorne; be termed cuprian faustite or aluminian chalcosi- Gunheath Pit, St. Austell, Cornwall, England, derite according to the current nomenclature rules UK; four localities in Germany: Herdorf, of the IMA CNMMN. Further, some nomencla- Siegerland, Hagendorf Slid, Bavaria; tural errors have been made in calling two Schneckenstein, Saxony; and Siegen, samples of planerite from Tras Pahang, Westphalia. It has also been found at the Lake Malaysia (Murthy, 1989) 'turquoise' and Boga quarry, Victoria, Australia. ' faustite' respectively.

107 E. E. FOORD AND J. E. TAGGART, JR.

Studies on coeruleolactite 5 or 10 wt.%) and X-ray diffraction studies of one of these areas showed the presence of crandallite. Valid specimens of 'coeruleolactite', the The ionic radius of Ca2+ is 0.99, significantly supposed Ca-dominant (A-site) member of the larger than the 0.69 for Cu2+, 0.76 for Fez+, and turquoise group, originally described by Peterson 0.74 for Zn 2+. It can be clearly seen that the ionic (1871), were sought for. Peterson (1871) radius of Caz+ is much larger (>20%) than any of described his material as being bluish milk- the other cations found in the A-site of turquoise. white in colour. Many different collectors and Fischer (1958) presented an analysis of a white museums were asked if they had material from the variety of 'coeruleolactite' from the Rindsberg type locality for 'coeruleolactite': Rindsberg, mine, Nassau, Germany, and based on the 5.09 Katzenelnbogen, Nassau, Saxony, Germany. wt.% CaO content and an X-ray diffraction None could be obtained, even by visitation of pattern that matched those for other members of the locality by Roland Dietrich and six other the turquoise group, 'coeruleolalctite' was stated people (Roland Dietrich, pers. comm., 1985). A to be a valid species. However, close examination former mineral dealer, Mr Forrest Cureton (Grass of the other components determined: H20 23.4 Valley, CA) had a piece of 'coeruleolactite' wt.%, P205 30.1, A1203 40.3, MgO 0.4, CuO 0.24 labelled 'coeruleolactine' from Katzenelnbogen. indicates clearly that this 'coeruleolactite' is a The handwritten label appears to be about 80-90 mixture and not one mineral; likely containing years old. The specimen was obtained from Scott crandallite and some wavellite and/or variscite as Williams Mineral Co., of Scottsdale, AZ, who had was found in the specimens that we examined. labelled it: "coeruleolactite -- rich blue massive Fischer (1958) presented Debye-Scberrer X-ray on limonite. Ausgebrannte Eisensteingrube, diffraction data for both white and coerulean-blue Katzenelnbogen, Nassau, Germany". This varieties of 'coeruleolactite'. He did not indicate specimen shows light-medium coerulean blue that contaminant mineral phases were also found. material, with sprays of colourless wavellite, on Dietrich (1978, 1982) identified what he thought a limonite matrix. X-ray diffraction analysis was 'coeruleolactite' from the Rotl~iufchen mine showed the presence of a member of the turquoise in Waldgirmes near Wetzlar, Germany. However, group with appreciable (20-30%) wavellite and the material does not have any Ca in it, and, while variscite as well. SEM-EDS study confirmed that nicely microcrystalline, and apple green in colour, the mineral was a heterogeneous mixture of at is a planerite containing some Fe and Cu. least three different minerals. An ICP-AES 'Coeruleolactite' was reported from the analysis (P.H. Briggs, USGS) of the X-ray Cruzeiro pegmatite, Governador Valadares diffraction split showed (in wt.%): AlaO3 35.9, district, Brazil, by Proctor (1985) who obtained CaO 0.15, FeO 0.18, P205 36.7, BaO 0.02, CuO this information from an article in the 2.75, Na20 0.04 K20 0.05 MnO 0.02, ZnO 0.20, Mineralogical Record by Cassedaune and Saner total 76.01. Allowing for the admixed variscite (1980). This material was identified on the basis and wavellite, it is clear that this specimen is a of X-ray powder diffraction data only. cuprian planerite. Material from General Trimble's Mine, East A second specimen of light blue-green Whiteland Township, Chester Co., PA was 'coeruleolactite' was also obtained from Mr originally stated to be 'coeruleolactite' by Genth Forrest Cureton, who obtained the specimen (1875) and later workers. McConnell (1942) from another mineral dealer, Mr David Garske. correctly pointed out that the material was not Mr Garske obtained the specimen from Hans J. 'coeruleolactite' but erred in calling it turquoise Wilke and Ilse A. Wilke who in turn obtained the based only on X-ray examination and without specimen (a dump sample) in Germany. A semi- chemical analysis. We obtained specimens of quantitative analysis (ICP-AES) showed only 0.3 'coeruleolactite' (Figs 7-8) from General wt.% CaO, approximately 3 wt.% Fe203 (all Fe as Trimble's Mine from the Rand Collection at ferric iron), and about 5.0 wt.% CuO. This Bryn Mawr College, and based on our X-ray and specimen is a turquoise-planerite. X-ray diffrac- complete chemical studies (Tables 2 and 3) have tion studies confirmed that the material was pure, shown the mineral to be essentially half-empty as did SEM-EDS studies. Minor colourless ~xrquoise but with vacancy dominating the A-site, wavellite (younger than the turquoise-planerite) thus dictating the proper name cuprian planerite. is also present. A few areas (SEM-EDS study) Unpublished X-ray studies by F. A. Hildebrand contained appreciable amounts of CaO (more than for W. Schaller (1952, internal USGS report) were

108 THE TURQUOISE GROUP

made for samples of planerite from Gumeshevsk, the type locality of rockbridgeite. Rocks and Syssert, Urals, Russia, and for 'coeruleolactite' Minerals, 57, 20-2. from General Trimble's mine, East Whiteland Belyaev, A.A. and Ievelev, A.A. (1990) Mineralogy and Twp., Chester Co., PA. The same sample of prospects of turquoise on Pai-Khoy. Abstracts, 15th planerite, USNM R5524 and one additional General Meeting of the International Mineralogical sample R5523 (from the same locality) were Association, vol. 2, 672-3, Beijing, China. examined by X-ray powder diffraction methods Boriskin, V.P. (1974) Zinc-containing turquoise of the by Hildebrand and both identified as planerite. Bukantau region (central Kyzylkum) (in Russian). The sample of 'coeruleolactite' (USNM R5610) Doklady Akad. Nauk Uzbek S.S.R., 31, 42-4. was termed coeruleolactite with some admixed Boriskin, V.P. and Kuzmina, S.V. (1976) Mineralization associated with turquoise deposits in the Bukantau variscite. Region. (in Russian) Zap. Uzbek. Otdel. Vses. Two samples of conchoidally fracturing dark Mineral. Obshch., 29, 63-6. olive green to blue green 'coeruleolactite' from Braithwaite, R.S.W. (1981) Turquoise crystals from the Royston District, Lyon County, NV (from Britain and a review of related species. Mineral. Wards Natural Science Establishment) were Record, 12, 349-53. studied and found to consist of material inter- Cassedanne, J.P., and Sauer, D.A. (1980) Famous mediate between planerite and chalcosiderite and mineral localities: the Cruzeiro mine past and about 15% admixed quartz. Less than 0.3 wt.% present. Mineralogical Record, 11, 363-70. CaO was detected. Cech, F., Povondra, P., and Slfinsk.9 (1961) Ober Planerit, aus Ponikl~t bei Jilemnice (NordNShmen) Acknowledgements und fiber die Beziehung zwischen Planerit, Coeruleolactit und Ttirkis. Neues Jahrb. Mineral., We wish to thank Edyth B. Engleman (USGS) Abh., 96, 1-30. and Larry L. Jackson (USGS) for Karl Fischer Cid-Dresdner, H. (1964) The crystal structure of water analyses. Thanks are due to D.L. turquois. Die Naturwissenschaften, 51, part 16, Williamsun (Colorado School of Mines) for 380-1. providing Mrssbauer spectra of three samples of Cid-Dresdner, H. (1965) Determination and refinement planerite and aheylite. Dr. Arnold Fainberg (now of the crystal structure of turquois, deceased) provided all of the infrared spectra for CuA16(PO4)g(OH)8.4H20. Z. Kristallogr., 121, turquoise group members. TGA spectra were 87-113. Cid-Dresdner, H,, and Villarroel, H.S. (1972) obtained by K.G. Esposito and C.G. Whitney Crystallographic study of rashleighite, a member of (USGS). We thank the various collectors, mineral the turquoise group. Amer. Mineral., 57, 1681-91. dealers, and museum curators who provided us Dietrich, R. (1978) Neues zur Phosphatparagenese der with such important material to characterize Grube Rotl~ufchen in Waldgirmes bei Wetzlar, Teil planerite, aheylite and coeruleolactite: Richard II. Aufschluss, 29, 139-53. A. Kosnar, Carl A. Francis, Juliet C. Reed, Dietrich, R. (1982) Neues zur Phosphatparageneses der Anthony R. Jones, Forrest Cureton, Victor K. Grube Rotliiufchen. Emser Hefte, Jg. 4, Nr. 3, Din, Frantisek Cech (now deceased) and Vandall 22-47. T. King. We thank Roland Dietrich for all of his Erd, R.C. Foster, M.D. and Proctor, P.D. (1953) efforts to obtain specimens of type coeruleolac- Faustite, a new mineral, the zinc analogue of tite. We thank Dr Akira Kato for his continued turquoise. Amer. Mineral., 38, 964-72. interest and encouragement on this project, both Fischer, Emil (1958) Ober die Beziehungen zwischen minerals having been submitted to the CNMMN Coeruleolactit, Planerit, Tfirkis, Alumochalkosiderit IMA while he was chairman. We also thank the und Chalcosiderit. Beitriige zur Mineralogie und following people for reviewing the manuscript: Petrographie, 6, Bd 6, 182-9. Peter J. Modreski (USGS), Richard C. Erd Foord, E.E. and Taggart, J.E. (1986) Reassessment of (USGS), Vandall T. King, and Henry L. the turquoise group: redefinition of planerite, Barwood plus two outside journal reviewers. ([7)A16(PO4)z(PO3OH)z(OH)8.4H20 and aheylite, FeA16(PO4)4(OH)8-4H20, a new member of the group. Abstracts with Program, the 14th General References Meeting of the IMA, 13-18 July (1986) Stanford University, Stanford, CA, p. 102. Barwood, H.L., and Zelazny, L.W. (1982) Phosphate Genth, F.A.L.K.W. (1875) Preliminary report on the minerals in the Vesuvius, Virginia, area and notes on mineralogy of Pennsylvania. Penna. Geol. Survey,

109 E. E. FOORD AND J. E.TAGGART, JR.

2nd series, Rep. B (1874). McConnell, D. (1942), X-ray data on several phosphate Giuseppetti, G., Mazzi, F. and Tadini, C. (1989) The minerals. Amer. J. Sci., 240, 649-57. crystal structure of chalcosiderite, Mitchell, R.S. and Freeland, H.R. (1978) Turquoise CuFe3+6(PO4)4(OH)8-4H20. Neues Jahrb. Mineral. from Virginia's Kelly Bank Mine. Rocks and Mh., 227-39. Minerals, 53, 214-8. Guthrie, G.D. and Bish, D.L. (1991) Refinement of the Miicke, A. (1981) The paragenesis of the phosphate turquoise structure and determination of the hydro- minerals of the Hagendorf Pegrnatite - A general gen positions. Geol. Soc. of America Abstracts with view. Chemie der Erde, 40, 217-34. Programs, 23, no. 5, p. A158. Murthy, K.N. (1989) The occurrence of turquoise and Hermann, R. (1862a) Ueber Planerite, ein Neues fanstite in Tras, Pahang. Bull. Geol. Soc. Malaysia, Mineral, Untersuchungen einiger neuer Russischer No. 23, 147-56. Mineralien. Bull. Soc. Imp. d. natur, d. Moscou, 35, Nikolskaya, L.V., Lisitsyna, E.E. and Samoiloviteh, M.I. No. 3, Part 1,240-3. (1974) Coloration of turquoise from the deposits of Hermann, R. (1862b) Section 64, Planerit. In Central Asia (in Russian). Izvestia Akad. Nauk SSSR, Materialien zur Mineralogie Russlands (N. yon Geologieal Series, no. 9, 105-11. Kokscharov), volume 4, St. Petersburg, p. 115-7. Petersen, T. (1871) Coeruleolactit ein neues Mineral von Ivanov, O.K. (1979) Zn-bearing alumochalcosiderite - Rindsberg, bei Katzenellenbogen, in Nassau and Zur first occurrence in the USSR (in Russian). Zap. Vses. Kenntnis der Thonerdehydrophosphate. Neues Min. Obsheh., 108, part. 6, 701-4. Jahrb. Mineral., 353-9. Jackson, L.L., Taggart, J.E. and Foord, E.E. (1985) A Pogue, J.E. (1915) The Turquois, a study of its history, quantitative determination of water in small mineral ineralogy, geology, ethnology, archaeology, mythol- samples: Pittsburgh Conference, New Orleans, LA, ogy, folklore, and technology. National Academy of 1985, Abstract, p. 1191. Sciences Memoirs, 12, part 2, 207 pp. Jackson, L.L., Brown, F.W. and Neil, S.T. (1987) Major Price, C. (1981) Turquoise crystals at Narooma, N.S.W. and minor elements requiring individual determina- Australian Gem and Treasure Hunter, no. 59, p. 43. tion, classical whole rock analysis, and rapid rock Proctor, K. (1985) Gem pegmatites of Minas Gerais, analysis. Chapter G: U.S. Geological Survey Brazil: The tourmalines of the Governador Valadares Bulletin, 1770, (P. Baedecker, ed.) p. G1-G23. District. Gems Gemology, Summer (1985) p. Khorassani, A. and Abedini, M. (1976) A new study of 86-104. turquoise from Iran. Mineral. Mag., 49, 640-2. Sehaller, W.T. (1912) Art. V. Crystallized turquoise Kunov A., Velinova, M., Punev, L. and Dragostinova, from Virginia. Amer. J. Sci., 33, 35-40. V. (1982) Cuprofaustite-a new mineral for Bulgaria Silaev, V.L., Yanulova, L.A., Kozlov, A.V. and (in Bulgarian). Geokhimija, Mineralogija, i Lyutoyev, V.P. (1995) Turquoise from the Urals- Petrologija, 16, 55-60. Paikhoy region. (in Russian) Proc. Russian Mineral. Kunov, A., Velinova, M. and Punev, L. (1986) Soc., 124, 71-86. Phosphate mineralization in the Spahievo Ore Field Sklavounos, S., Ericsson T., Filippidis, A., Michailidis, (Eastern Rhodope Mountains). From Crystal K. and Kougoulis, C. (1992,)Chemical, X-ray and Chemistry of Minerals- Proceedings of the 13th M6ssbauer investigation of a turquoise from the General Meeting of the IMA, Varna, Sept. 19- Vathi area volcanic rocks, Macedonia, Greece. 25,1982. Bulgarian Academy of Sciences Neues Jahrb. Mineral. Mh., 469-80. Publishing House, 877 89. Smith, A.E., Jr. (1985) Aluminum phosphate minerals Lichte, F.E., Taggart, J.E. and Riddle, G.O. (1983) from Mauldin Mountain, Montgomery County, Analysis of minerals by inductively-coupled plasma- Arkansas. Mineralogical Record, 16, 291-5. optical emission spectroscopy. Lab Corn West, May, Turesebekov, A. Kh., Golovin, A.F., Balakin, V.V. and 1983. Ismailov, M.A. (1979,)Turquoise and its mineral Lichte, F.E., Golightly, D.W. and Lamothe, P.J. (1987) paragenesis in a copper-porphyry deposit of Inductively-coupled plasma-atomic emission spec- Kalmakyr (Ahnalyk ore field, Uzbek S.S.R.). In trometry, Chapter B. U.S. Geological Survey Russian. Zap. Uzbek. Otdel. Vses. Mineral. Obshch., Bulletin, 1770, (P. Baedecker, ed.) p. B1-B10. 32, 64-9. Matsubara, S. and Kato, A. (1987) Phosphate minerals Van Wambeke L. (1971) The problem of cation from Fubasami Clay Mine, Tochigi Prefecture. deficiencies in some phosphates due to alteration Abstr. Annual Meeting of the Mineral. Soc. of processes. Amer. Mineral., 56, 1366-84. Japan, Tokyo, 113 (in Japanese). Yakontova, L.K., Soboleva, T.V., Plyusnina, I.I., Matsubara, S., Saito, Y. and Kato, A. (1988) Phosphate Sergeeva, N.E. and Pozdnyakova, N.V. (1989) The minerals in chert from Toyoda, Kochi City, Japan. J. Techutsk deposit - mineralogy and genesis. In Min. Petr. Econ. Geol., 83, 141-9. Russian. Zap. Vses. Mineral. Obsch., 118, 83-93.

II0 THE TURQUOISE GROUP

Zang, H. and Lin, C. (1984) Magnetic properties, characteristic spectra and colors of turquoise. [Manuscript received 6 March 1997: Geochemistry, 3, 322-32. revised 20 May 1997]

III