Thn Amerrcew Mrneralocrsr

THn AMERrcew MrNERALocrsr

JOURNAL OF THE MINERALOGICAL SOCIETY OF AMERICA

Vol. 53 JULY-AUGUST, 1968 Nos. 7 and 8

POUGHITE, A NEW TELLURITE MINERAL FROM MEXICO AND HONDURAS

Rrcnenn V. G.LrNos,Hofecker Road,,R.D. fi|, P ottstown, P enns yll an'ia. Assrnecr A ner,r'hydrous basic ferric tellurite-sulfate Fez(Teos)z(Son).3Hro has been found at the Moctezuma Mine, Sonora. It is identical with an unnamed mineral from Honduras partially described in 1944 by Frondel and Pough. The mineral is yellow to greenish yellow in color, orthorhombic a:9.66, b:14.20 and,c:7.86 A, with a habit and cleavagesimilar to baite. H:2+; G:3.75. Principal lines in the X-ray powder pattern are 7.IO (10), 5.74 (10),3.239 (7),3.564 (6), 3.336 (6), and 3.053 (6). The name is for Frederick H. pough.

IwtnonucrroN In 1944 in an article on two new tellurites of iron, mackayite and blakeite, Frondel and Pough mentioned a further new iron tellurite from Ilonduras, of which insufficient material was found for a complete de- scription. This mineral had first been observed by Dana and Wells in 1890 and thought to be tellurite; Larsen in l92l further studied the mineral, which he mistook for "durdenite" (emmonsite). No further work was done on this new unknown mineral, but its macroscopicdescription and especially the d-values for its powder photograph published in that article enabled the author to establish its identity with material found at the Moctezuma mine in Sonora,Mexico. The name poughite is proposed for this new mineral.

OccunnBwcB Up to the presenttime poughite has been found by the writer in only two specimens.One, from the mine dump, is a piece of limonite-stained qttartz breccia abundantly coated with drusy crusts and small botryoidal rosettes of a brownish yellow mineral. The only other mineral on the specimen besides poughite, quartz, and limonite, is pyrite in small amounts in corroded grains which are in the course of being altered to Iimonite. The second specimen is a piece of vein quartz coated along cracks and in vugs with emmonsite and minor limonite. In one area there are some corroded pyrite grains, and in this area the emmonsite is 1075 1076 ITICIIARDV. GAINI.S replacedby a crust of greenishyellow crystalsof poughite.Othcr minerals on the specimenare an undescribeduranyl tellurite and fine crystals of jarosite perchedon hairs of emmonsite.

PnoprnrrBs Physical and,optical properties.In the specimensfound poughite varies from dark yellow to brownish yellow and greenish yellow. Synthetic poughite is pale yellow to bright sulfur yellow. Hardnessis about 2|. Cleavage(010) is perfect and (101) good. Specificgravity, measuredby pyknometer on synthetic material, varied between3.70 and 3.80 and the averageof three determinationson difierent sampleswas 3.758' Poughiteis biaxial negative,with 2V about 15o-20o.Indices of refrac- -t tion area : 1.72 0.01,B : 1.985+ 0.01,and r : 1.990+ 0.01.Pleochroism is strong: X: colorless, Y :pale greenish1'ellow, and Z: pale yellow' X is parallel to 6, and I/ parallel to o.

Chemicallesls. Poughite is easily soluble in hydrochloric acid and slowly so in hot dilute sulfuric acid. X-ray fluorescenceanalysis showed the presenceon only iron and tellurium. When a drop of barium chloride solution is added to a hydrochloric acid solution of poughite, a milky white precipitate forms, indicating the presenceof sulfate in the mineral.

CompositionSince it was not felt desirableto sacrificethe two specimens found for chemical analysis, even though such a coursewould have pro- vided at least 100 mg of material, it was decidedto try to synthesizethe mineral. An additional reason for this approach was the unsuitability of the few crystalsfound for measurementor X-ray work, and it was hoped that some suitable onescould be made. Initial effortswere unsuccessfulbecause the presenceof sulfatein the compositionand the necessityof providing sulfate ions among the raw materials for s1'nthesiswere not recognized. Finall-v, sulfuric acid was added to the ingredients in an effort to duplicate the conditions in an oxidizing pyritic orebody, and with this addition the compound was formed easily. Best results were obtained by using stoichiometric quanti- ties of TeO2,Fe(OH)e, and HzSO+at about 240oCand 33 bars, in pyrex tubes within a stainlesssteel pressurevessel. Above 255oCa new compound in the form of honey-brown triclinic crystals forms at the expense of the poughite. This compound was analyzed and appears to be a hydrous basic ferric tellurite, probably Fer(TeOr)z(OH)2'2H2O. Considerabletrial and error was necessarybefore it was possibleto determinethe correctproportions of Fe, Te, and SOn: in the compound and make a product which gave a powder pattern free from lines repre- POUGHITI], 1077

Tarm 1. Qummrrlrrlc Cnrnrcar, Ax.lr,vsrs ron Poucnrrr

Synthetic poughite Fer(TeO3)r(SO4)'3HrO

FezOr 26 34 26.O5 TeO: 50.56 52.08 SOr 12.32 13.06 HrO 9.40 8.81 Insoluble 0.97

Total 99.59 100.00

Note: The insoluble in the analysis consisted of glass fragments from the pyrex tube. senting extraneous compounds. When this was finally accomplishedthe synthetic product was analyzedby conventionalwet chemicalmethods. The resultsof this analysisare given in Table 1. The resultant formula, Fer(TeO)r(SOa)'3HzOis the first compoundto be recognizedinnature in which the tellurite radical is in combination with other anions'

Cnvsr,qr,rocRAPHY Morphology. Crystals of poughite are orthorhombic, diamond shaped, with a tabular habit similar to that of barite. The tabular crystals are flattened parallel to (010). Forms observedwere (010), (101)' (011)' (120), and (100) (Table 2).

X-ray powd,erd,ifiraction data. Powder photographs of both natural and synthetic poughite give a pattern in which the six strongestlines, in order of decreasingintensity, are 7.10,5.74,3.239,3.564,3.336, and 3.053.It will be noted that in the original listing of the spacingsfor this mineral, publishedin 1944,the three strongestlines are given as 3'34, 5.74, and

Ttpln 2. Poucurrr ANcr,n T.lsr-n Orthorhombic@: b: c:0.6803: 1.000:0.5535 io: Qo:.ro:O'8136:0.5535: 1.000 qtih: fu : 0.6803: 1.2291 : 1' 000 rz:P2;q2: |,8067: 1.4699: 1.000

Forms

6 010 0000/ 90000' 0000' 90000' a 100 90000' 90"00' 000 90"00' I 120 36 19 90 00 000 36 t9 53 41 / 011 000 61 02 90 00 28 58 90 00 r 101 90 00 50 52 39 08 90 00 39 08 1078 RICHARD V. GAINES

1.87.The reasonfor this, which becomesobvious from inspectionof the reproduction of the powder photograph in question,is that this photograph is heavily fogged in the region of high d-values, and thus it was impossiblefor the original investigatorsto properly estimate the inten- sitiesof the lines in this region.A completelist of the spacingswith cor- responding hkl values is given in Table 3, and from this it becomesclear that the mineralsfrom Honduras and from Sonoraare identical' Precessionphotographs were taken of the h}l, htl, h2l, hkU, and,hkl planesof poughite.From thesephotographs, and with further refinement of the cell dimensionsbased on the powder data, it was determinedthat poughite is orthorhombic, space grottp Pmnb, and that the cell dimen- riotri ut.' a:9.66 L,b:t+.zOA, and c:7.86 A, ail dimensions*0'02 A. The cell volume for poughite is 1078.2A3 and Z:4. The calculated specifi.cgravity is 3.775,in good agreementwith the averagemeasured value of 3.758.

Taslr 3. INnrxlo X-Rlv Poworn Dera ron PoucHtrt a:9.66 A, u:t+.zO A, c:7.86 A Cu radiation, Ni filter

tl; It: d(meas)A d(calc,rA npt d(meas)A a(*t.)A tenslty. tensrty

10 7.t0 7 100 o20 L 2.053 2.052 261 I 6.tl 6.097 101 z 2.03+ 2.036 +r2 10 5.74 5.72r r20 I 1.93r 1.925 171 1 4.82 4.830 200 1 1.906 1.908 114 1 4.62 4.626 t2l 2 1.872 | .876 501 3.926 3.930 002 2 1.858 1.858 124 1 J,rt 3.739 IJI I 1.819 t.820 20+ 6 3.564 3.560 221 L 1.782 1.780 M2 6 3.336 J.JJI 140 z r.764 r.762 +r3 3 239 3.239 122 2 1.746 180 6 3.053 3.048 202 2 r.719 |.723 423 212 2 1.697 1.693 lM 4 2.983 lz.ost I 2.980 301 2 1.661 1.659 s41 5 2 -940 2 g33 320 1 r o.t.t 1.630 281 2.869 2.8ffi 240 1.595 2.806 2.801 222 z 1.558 z 2.757 2.748 321 2 1.543 2.639 2.634 042 I 1.519 1.519 523 5 2.543 2.542 142 z I .4 /.) 2.354 2 350 322 3 r.448 ( t ca.c 34r 1 |.424 2 2.279 \2.273 213 J t.4tl 2.203 2.201 r61 I 1.220 2.r30 2.125 zffi 3 1.180 POUGHITE r079

T,q.sln 4

Specilic Strongestpowder Composition Symmetry gravity lines

Emmonsite Fer (TeOr)a 2HrO Monoclinic? 4.55 3.12,5.78,3.60 Mackayite Fer (TeOr)a 5HzO Tetragonal 4.69 3.327,3 .17,4.95 Sonoraite FqTerOr (OH)r.HzO Monoclinic 3.95 10,40,465,3.099 Poughite Fer (Teoa)r(SO, .3HrO Orthorhombic 3. 78 7.1o,5.74,3.329 Blakeite ?? 3 00, 2.54, 1.72 Artificial Fer (TeOr)r Fez (TeOr)s ?? 1.71,3.27,2.54 Artificial Fe (TeOr) (OH)'HzO FeTeQ (OH).H:O Triclinic 4.79 2.94,3 36,4.t\

Table 4 lists the principal constants of the five iron tellurites which have up to now been observedin nature, plus those of two artificiai com- poundswhich may well be found in the future. It will be noted that the strongest powder lines for mackayite and emmonsite also differ from thosepublished in the 1944article. The reasonfor this is the sameas in the case of poughite.

NeuB The name poughite (pronouncedp0'AIT) is proposedfor this mineral in honor of Dr. FrederickH. Pough,for his many valuablecontributions to the scienceof mineralogy over a span of thirty-five years, and for his collaboration in the first study of this mineral from Honduras.

TvpB Mern'nrar Since this mineral was first found in lfonduras, the El plomo Mine, Ojojona District, Tegucigalpa,Honduras must be consideredthe type locality. Material from this find is in the mineral collection at Harvard University. Poughite from Moctezuma, Sonora, Mexico, upon which the presentdescription is based,is neotype material, a specimenof which is preserved in the collection of the U. S. National Museum, Washington, D. C.

AcrNowr,BocwNrs

The writer wishes to express his appreciation to rng. G. p. Salas, Director of the rn- stituto de Geologia of the National university of Mexico, under whose auspices this work was undertaken and to Quim. Alberto obreg6n, for chemical analyses. The mineral poughite has been approved by the commission on New Minerals and Mineral Names, r.M.A.

REFERENcES

DeNl, E' S. awo H. L. wnr.r.s (1890) on some selenium and tellurium minerals from Hon- duras.Amer. f .\ci,.,40,78. FnoNnu, c. eNo F. Fr. Poucn (1944) Two new tellurites or iorn: mackayite and blakeite, ,,durdenite,'. with new data on emmonsite and Amer. Mineral,.,2gr 2ll-225. 1O8O RICIIARD V. GAINES

G,uNus, R. V. (1965) Nuevos clatos sobre mackayita' Botr' Soc. Geol'.Metc.,28 (No' 2), 75-82. Garr,.ns R. V. (1965) Mineralizaci6n de telurio en la Mina Moctezuma, cerca de Mocte- zuma, Sonora. [Jnia Nac. Autdn. M6rico, Inst Geol,Bol'.,75rpt. l. LARSEN, E. S. (1921) The microscopic determination of nonopaque minerals. tl. S. Geol,. Sura., Btill 679.

Monuscript receiaed,October 20 , 1967; aeceptedJor publication, December6' 1967'