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Papagoite, a New Copper-Bearing Mineral from Ajo, Artzona*

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Papagoite, a New Copper-Bearing Mineral from Ajo, Artzona* THE AMERICAN MINERA]-OGIST, VOL. 45, MAY-JUNE, 1960 PAPAGOITE, A NEW COPPER-BEARING MINERAL FROM AJO, ARTZONA* C. OssonNn llutrow, StanJord'(Iniaersi'ty, Stanford', California, .qNpANcBr-rN.q, C. Vr-rsrors, U. S. Geologi'colSuroey, Washington,D. C. AssrRAcr thereof. to (100) was noted in thin sections but it was not evident in crystals or fragments Papagoiteismonoclinicprismatic,spacegroup Cm,C2,otC2fm,witha:12'9lA'b:ll'48' pattern is re- ,:+.05, all values +0.01 A; g:100'38'; aibic:1.124;l:0.408. A powder of the five corded and it has been indexed up to 2A-65o; the d-spacings and intensities (8)' strongest lines are: 2.874 i\ G0), 4.29 (9),2.204 (9),2.795 (8), and 3 '44 The mineral has a cerulean biue color in hand specimen and is distinctly pleochroic. : -a : 2Y : 78" dispersion faint' Biaxial, negative; a : 1.607, B : l'641, t l'67 2, 7 0'065; ; r)v;X:very pale glaucousgreen to colorless,Y: cendreblue, Z:Venice gteen;ZlYlK; to the Xnr:++" both in the acute angle,and Z:b'Y is very nearly normal "iXnd:35', 4 { CaCuAl[SiOr],(OH) ' I . in which The mineral has been named for the Indian tribe that once inhabited the region the mining center of Ajo, Arizona, is situated' Occunnoncr The papagoite-bearingspecimens were found at Ajo, Arizona, in an isolatedpocket 150ft. below ground-levelat the 1750level in an areathat has now been entirely removed. The nearest high-grade sulfide ore now lies 50 ft. below and 1000ft. eastof the papagoitelocality' and calcite, and minor quantities of apatite that is weakly dichroic, * Publication authorized by the Director, U. S. Geological Survey' 599 C. O, IIUTTON AND A. C. VLISIDIS I mm. Frc. 1. veinlets of papagoite in an assemblageof clear quartz and dusty albite; the black areas are manganese and iron oxides and hydroxides. The small patch of fibrous material near the center of the drawing is ajoite. Ajo, Arizona. stumpy crystals of rutile, sphene, slightly metamict zircon, tiny well- formed, sharply pyramidal crystals of anatase,alunite, and patches of brown manganeseand iron hydroxides;rare tenorite may alsobe present in thesebrown areas.Sulfides were not detectedin the material examined. clearly the specimensare the product of metasomatismbut, sinceno rel- icts of the original unalteredmaterial remain, one is unable to say if the specimenshave beenderived from the monzonitelitself. The mineral describedherein has been named papagoite2after the rndian tribe that inhabited the areain which the active minins centerof Ajo is situated. Puysrcar- PnopBnrrBs In hand specimen, the color of papagoite is very close to Ridgway,s ceruleanblue (Ridgway's Plate 8,45. BG-B), and in thin section,or in crushed particles with a thickness of about 0.03-0.04 mm., a strong pleochroismis evident.The following optical data have beendetermined: a:1.607, +0.001,0:I.641, t:1.672,7-a:0.065; X:colorless to very 1 For comprehensive studies of the geology of Ajo, Arizona, in particular, and the region in general, the reader is referred to the work of J. Gilluly (1931 A, lg37 B, 1946). ' PAPAGOAIT (Royal Geographic Society (R.G.S. II) System); pepagoite (American usage). PAPAGOITE,A NEW COPPERMINERAL 601 pale greenish-blue(pale glaucousgreen, Ridgway's Plate 33, 39" . B-G, f), Y:blue (cendreblue, Ridgway's Plate 8,43. G-8, b),Z:deep green- ish blue (Venicegreen, Ridgway's Plate 7, 41. BB-G, b). Z>Y>X. 2V:78" *1o, and negative optic sign. Dispersion is exceedinglyfaint with r)v. The extinctionangie Xr\6:44o, or X/\a:35o, both in the acuteangle, whereas YAc:46o. Y to the perpendicularto (001) is ap- proximately36". Z:b (Fig. 2). If crystalsthat exhibit prominent developmentof the form [201] are orientedin mounting media with (201)parallel to the microslide,slightly Frc. 2. Optical orientation of papagoite from Ajo, Arizona. The plane of the drawing is perpendicular to the b-crystallographic axis [:7]. off-centered optic normal interference figures are observed. The refrac- tive index 7 and a value very closeto d. may be measuredwhen a crystal is oriented in this fashion, whereasfor crystals lying on the dominant face in the zone [0101,aiz., (001), the appropriate vibration directions havethe refractiveindices a':I.615 and'y: l.672.Thisis the mostusual aspectassumed by crystal fragments in immersion media if the appro- priate face in the zone [010] has not been destroyedduring removal of crystals from matrix. If crystal fragments should lie on (401), then the refractive indices are equivalent to ? and a value almost equal to a. The mineral has a hardnessof about 5-5|, that is, it may be scratched by adularia but not by apatite, and the specificgravity at 19oC. of the analyzed material was determined to be 3.25 by centrifuging the powder in bromoform-diiodomethane mixtures.During separationof papagoite from the matrix the specific gravity of any one fraction did not vary from 3.25 by more than 0.005. A distinct cleavageparallel to (100) is evident, but this is to be seenonly in sectionsof papagoite that have 602 C. O. HUTTON AND A. C. VLISIDIS been carefully oriented and cut parallel to a plane perpendicular, or nearly so, to the vertical crystallographicaxis. Cnvsrerr,ocRApHy Only partially complete crystals were available to the writers and these were found in occasional vugs in qvartz veinlets; none exceeded 0.75 mm. in length. Although they were detachedfrom the walls of the host with care no completeeuhedra were found. Crystals tend to be slightly elongatedparallel to the b-axis,the domi- nant zoneaxis, and somewhatflattened parallel to {001}. AII facesin the Frc. 3. Typical crystals of papagoite from Ajo, Arizona. zone [010] are strongly striated parallel to the zone axis. Goniometric measurementsyielded data that lacked desirablepreciseness on account of oscillatory combination of faces,but more so becauseof the presence of satellites and accessoriesthat may depart as much as 4o from the orientationof the planeswhich support them (Fig. 3A, C). Only one gen- eral habit was found, and in most of the crystals observed c[001], g{a01}, and mt110} are dominant (Fig. 3C). Other facesin the zone [010]are dll}2l, elt}ll,f{201}, htt60ll,and a1100}.The dominanceof c{001} and d{1021, or sometimesfl2}ll, and a marked suppressionof o[100] Ieadsto crystals that are tabular in form (cf. Fig. 38). Facesof the form mlI10\ are, for the most part, devoid of satellitesand striations and consequentlythey yield good reflections.The satellitesare clearly PAPAGOITE, A NEW COPPER MINDRAL 603 Tnst,e 1. Irqrnnrecrnr. ANcr,rs ron Pep,l^corrn Meas. angles No. of meas' made Calc. angles* 100n110 47"30', 47"50', 001n102 10' A 9050' 102n101 A 8'40', 101n201 13'30', 13044', 201n401 160 A 16'10' 401n601 8'30', 8"25', 601n100 22"30', 2 22"35', 110A110 84" 84"15', 110n001 83' q 82'55', * Since the unit cell dimensions from e-ray data are considered to have an accuracy of This one part in 1,000, the calculated angles in this column are given to the nearest 5'- argument applies to the angles listed in Table 2 also. the result of crystal growth, sinceno indicationsof etch phenomenaare apparent. Pyramidal faces appear to be absent from the nine crystals that were availablefor study. Goniometric measurements,which are consideredto have an accuracy that is no better than *30', are given in Table 1, where thesedata may be comparedto the interfacial anglesthat have been derived by caicula- tion from cell dimensionsyielded by single-crystal n-ray work' The values listed for the measuredangles are, in eachcase, averages of severalmeas- urements. The data securedby goniometric measurementlead to an interaxial ratio of aib:c:1.109: 1:0.415with B: 100o30',compared to the data derived from fr-ray measurements' ai,z', a:b: c: l'124521:0'4085' Tnnle 2. Sre.Nl.tnnANcr,n Tesre ton P'tpacotrr Monoclinicprismatic. a:bic:1.12+5i 1:0.4085;g:100'38'; poiQoiro:o.3632:0.4015:1; : rzipz: qz: 2.4906:0.9046 : | ; p : 79" 20' ; ps' : 0.3695, q6': 0.4085,ro' 0'1877' 6z Pz:B A c 001 90"00' 10'40' 79"20', 90'00' 0"00' 79"20', o 100 90"00' 90"00' 000 90 00 7920 000 m l1O 42 l0 90 00 000 42 r0 825s 47 50 e l0l 90 00 29 lO 60 50 90 00 1830 60 50 47 ro J 2o1 90 00 42 50 47 r0 90 00 32 r0 g 401 90 00 59 00 3100 90 00 48 25 31 00 h 601 90 00 6725 2235 90 00 56 50 2235 d toz 90 00 2025 69 35 90 00 950 6935 604 C. O, HUTTON AND A. C. VLISIDIS 0:100'38'. On the basisof the latter, the standard angles,Iinear, axial, and polar ratios,etc., have beencalculated and presentedin Tabie 2. X-n,c.y sruDy- considerable difficulty arose when attempts were made to orient crystal fragmentsfor single-crystalstudy becauseof the developmentof satellitesor accessorieson each crystal. Even fragments that measured about 0.1 mm. in diameter yielded r-ray difiraction patterns that one would expectto find for polycrystallinematerial. rn the simplestcase, it was possibleto orient the fragment so that straight, parailel layer Iines yielded by the host were dominant, but, at the same time, were con- siderably obscured by reflectionsdue to satellites whose orientations differedfrom that of the host by as much as 4o in some instances.This situation was most seriousfor rotations about the a and.baxes, since the reciprocalspacings perpendicular to thesedirections are relatively small, with the result that layer lines are crowded.
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