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Home , Adamite, Arseniosiderite, Conichalcite, Durango, Ojuela

FROM THE MINE, MAPIMI, * Menv E. MnosBl wrrn Norns oN rHE Occunnpwce sv Dew E. Mevpns2 eup FnnNcrs A. Wrsn3

Alsrnect

Adamite of unusually pure corrposition is described from a new locality, the Oiuela mine at Mapimi, Durango, Mexico. A chemical analysis is given together with measure- ments of the morphological axial rutio (a:b:c:O 9753:1:0.7055), the unit cell dimensions (os:8.30, bo:8.51, co:6.04 A), the specific gravity (4.435) and optical constants (X :1.722,Y:1.742, Z:1.763,2V (meas.)88"1-2'). Analysis gaveZnO 56.78,AsrOs 38.96, SiO, 0.26, H:O 3.53; total 99 53. Spectrographic analysis also revealed Cu (-g'1;, p5 (-0.1), Fe (001-0.1), Mg (0.01-0.1),Al (-9.91;, Ca (-6.91;, Ag (0.001-001) and Ga (-0.001). Cnvsrerr,ocRAPHY Most of the crystals of Mapimi adamite occur merged together as radiating crusts or as fan-shaped rosettes on a matrix of . A few

Frc. 1. Adamite crystal from Mapimi showing all the forns observed. single-crystals,however, were found. The crystals are elongated parallel to [010]. Most crystals were attached at one end of the &-axis;only three doubly terminated crystals could be found. These indicated holohedral symmetry. A test for piezoelectricity by the cathode-ray oscilloscope method gave negative results. The crystals range in size from j mm. to 8 mm. along [010]. The crystals are rather simple in habit. The form d{1011is dominant and is truncated by t1120\ and ml 110]. On some crystals the prism hl2I\l occurs,but only as very small faceswhich gave poor signalsdur- ing goniometric measurement,and D{010} was observedin several in- stances.The faces in the [010] zone are highly striated parallel to [010], producing a train of signals which made accurate measurementsimpos-

* Contribution from the Department of and Petrography, Ilarvard Uni- versity, No. 298. 1 Boston University, Boston, Massachusetts. 2 Harvard University, Cambridge, Massachusetts. 3 American Smelting and Refining Co. M9 450 MARY E. MROSE, DAN E. MAYERS AND FRANCIS A. WISE

sible. A somewhat idealized drawing showing all of the forms observed is given in Fig. 1. Although a great number of crystals were carefully examined, only nine of the very best of these were selectedfor measurement (Table 1).

TesLE 1. Aoeurrl' : Mnasunno eNo Cer,culamn ANcr-ns

No No Measured Range Forms of of Qual- itv* XIs M il"'l6zpz

1 1 VS c 9 18 M B 9 18 S D 45"11,-46 32

9 14 VS r, 63 42 -64 t4 9 36 L B 53022'-5+o59'

* A equals first quality

The linear elementsderived from these measurements(a:b:c:0.9753: 1:0.7056) are identical with those derived from c-ray Weissenberg measurementson the samecrystals (a: b: c:O.9753 : 1 : 0.7055). A number of other investigators have reported elements for adamite from other localities and these are listed in Table 2.

TnrrB 2. ReponrBo Monpnor,ocrclr, Elrupxrs or Areurre

Investigator Locality Axial Ratio

1. Des Cloizeau(1878) Chanarcillo, Chile dibie:0 .9733i1:0. 7158 2. Aloisi (1909) Mte. Valerio, Italy a:b:c:0 .9736'.1:0. 7013 3. Staples(1935) GoId Hill, oib:c :0.97 42i1:0. 7095 4. Mrose (1948) Mapimi, Mexico a:bic:0 .975311 :0.7055 5. Rosickf(1910) Thasos, Turkey atb.c :0.97 64iI i0.7049 6. Ungemach(1921) Laurium, Greece ai b: c : 0.977 01 1 t0.7 124 7. Des Cloizeauand Lacroix (1e10) Laurium, Greece aibic:o .9784:.l:0.7ll7 8. Kukharenko(1939) Northwestern Balkhash region (lilac variety) a;btc:0 .9787:l:,0 .7128 9. Palache(priv. comm.;1921) Laurium, Greece a:bi c :0.9812i1 :0. 7108 10. Laspeyres(1878) Laurium (emerald-green; cuprian) aibi c:0.9958i1 :0. 6848 Laurium (colorless) a:btc :0.99s8i I io.717 6 11. Murdoch (1936) Chloride Clifi, Calif. (colorless) aibic:0.996:1:0.718

The wide variation observed appears to be due largely to the poor quality of the measured crystals. In part, however, the difierencesmay be due to variation in chemical composition such as substitution of Cu or Co for Zn or of (POa)for (AsOn),but no definite correlations could be ADAMITE FROM MAPIMI, MEXICO r+J -t established.Laspeyres (1878) has shown that the angles of the adamite crystals from Laurium vary measurably with the presenceof Cu in sub- stitution for Zn. The arithmetical averageof the linear elementsreported, after eliminating those of Laspeyres (1878), Murdoch (1936) and Des Cloizeau (1878), which are relatively far out of line with the others, is a:b:c:0.9769:1:0.7086.An angle-tablefor the forms observedon the Mapimi crystals calculated for these elementsis given in Table 3.

Tasrn 3. AlAltrr: ANcr.r Teslr

Orthorhombic; dipyramidal-2 /m 2/m 2/nt a:bic:0.9769:1:0.7086; po:qoiro:o.7254:0.7086:1 Qt:r i fu: 0 .97 69 : 1. 37 86 : | ; rzifzi qz: | .4ll2 : I 0236i I Forms: Q p:C 6r pl--A 6z pz:B b 010 0'00' 90000, 90'00' 90'00' 0'00' t 120 27 06+ 90 00 90 00 62 53+ 0'00' 27 06+ m 710 45 40i 90 00 90 00 M 19+ 0 00 45 40'

h 2r0 63 58 90 00 90 00 26 02 000 6358 d r0l 90 00 35 57; 0 00 54 02+ 5402+ 90 00

Pnvsrc.q.rPnoprnrrrs [101] good. The {010} cleavagereported by Staples(1935) on crystals from Hill, Utah, was not observed. un- even. Brittle. Hardness3+. G.:4.435 +0.005 (an average of measure- ments of 8 difierent crystals on the microbalance); 4.435 (calculated). The specific gravity found for the Mapimi adamite, which is essentially pure Zn2(AsOrOH) is comparable to the values 4.475 and 4.484 re- ported by de Schulten (1903) for the pure artificial compound and by Rosickf (1910) for pure adamite from Thasos, Turkey. Lower values, rangingbetween 4.319 and 4.35,have beenfound for material containing Cu, Co or Fe" in substitutionfor Zn. Luster vitreous. Small crystalson the specimensare nearly colorless,while the larger crystals are greenish- yellow; all are transparent. The Mapimi adamite fluoresces a bright lemon yellow with a pale lemon yellow phosphorescencein short-wave ultraviolet radiation; a much weaker reaction is given in long-wave ultra- violet and in r-rays (pale bluish-green). Specimensfrom other localities react variously. A blue-green Laurium specimen gave a weak greenish fluorescencein both long- and short-wave ultraviolet; bluish-green, in K-rays. Negative results were obtained with a colorlessspecimen from Laurium, a blue-greenspecimen from Gold Hill, Utah, cobaltian material from Cap Garonne, France, and , Africa, and with cuprian ma- terial from Tsumeb. 452 MARY E, MROSE, DAN E, MAYERS AND FRANCIS A. WISE

-;j ?.

aE.q1 ^ =Y - d MJ

hF

2'* 95€ .3i*, * 'Ac=-.o^9^ --i -i -i ri 3 ;;

+t +t +l

\llo u =t Nh h **- 9 -- +r:9 o o o r/ /\ N € . . .n \ 6€ +t +l +l

J I

,Hj i --* X ^ N++ il f9<*

3 x -6- E s 888- 3* ???" HE ii A^ : s B f 3S g;E i :::l,i

EE9* p : ooo rl 9 o o P 9= E {,3r:i H9lhr >9 * .'- lRFii5, s-vs.'x' F J -J-jxI 333.59 €€o fr F" 833- p E F A ooo il o o E ! +r+r+r N.: o u aq E]' ppsi I €qEIs u Jr.ix'.' E=9,9R F

F ooo6:1 nnnr; o R$3 ? s -.; r' ..i x i e A

-- .i.: o a -.Uo."9Eix>sE'E .9E F.X* CJ UlH dN ADAMITE FROM MAPIMI, MEXICO 453

Oprrcar Pnopnnrtps The optical properties of the Mapimi adamite are cited in Table 4 in comparison with those reported on material from other localities. The wide variation in the indices of refraction is due to variation in the chem- ical composition of the crystals, as is clearly shown by comparison of the data on the cuprian and cobaltian material from Tsumeb, but since chemical analyses are lacking in most instances the nature of the rela- tionship is not clear. X-Rav Srunv A selectedsingle-crystal of the Mapimi adamite was studied by the Weissenberg r-ray method. The unit cell dimensions, given in Table 5, are in close agreement with those obtained by Strunz (1936) and Kok- koros (1937) on adamite from Thasos and Laurium. The Weissenberg films exhibited orthorhombic centro-symmetry. If the crystal class is

TAslo 5. UNrr Cnr,r Druoxsror.rsol Almrrrn

1 .t Adamite (Mapimi) Adamite (Thasos) Adamite (Laurium) (Mrose, 1948) (Strunz, 1936) (Kokkoros, 1937)

&o 8.30+0.02 8.32 8.31 bo 8.51 + 0.02 8.54 851 Co 6.04+ 0.02 6.08 6.06 asibsics 0.975:1:0.706 0.974:l:0.712 0.977:lto 712 ao/co 1.38 1.37 1.37 Vo 427 431 429 Space group Pnnm Pnnm Pnnm taken to be dipyramidal, as is indicated by the form development (sum- marized by Ungemach (1921)) and by the absenceof piezoelectricity, the spacegroup is establishedby the diffraction effects as Pnnm in conform- ance with that earlier reported. The spacing data obtained from a powder photograph of the Mapimi material are listed in Table 6. Photographs of the adamite pattern and of the isostructural species , Cuz(AsOd(OH), and libethenite, Cuz(POa)(OH),are given by Richmond (1940). Powder photographs taken of unanalyzed cobaltian and cuprian adamite from Tsumeb were found to difier very slightly in the relative spacing of the lines from that of the Mapimi material and to have very siightly smaller cells. CnBursrnv A chemical analysis of the Mapimi adamite, cited in column 2 of Table 7, proves it to be essentially pure Zn2(AsOr(OH). A semi-quantitative 4.)+ MARY E. MROSE, DAN E, MAYERS AND FRANCIS A. WISE

Tesrr 6. X-Rey Powpnn D.a.ra oN ANALvzED Aonurrr rnou Mlprur radiation, filter

No. d (meas.) d (meas.) d (meas.)

t6 5.94 IJ n in1 25 3 1.658 2 0.5 5.479 14 2.359 26 t t.622 39 4.897 1( 2.072 27 8 1.608 46 4.242 16 2.016 28 3 1.581 54 3.782 r7 1.958 29 3 1.570 62 3 .058 18 1.912 30 4 1.511 79 2.967 19 1.888 31 4 1.483 88 2.698 20 1.851 32 0.5 t.462 94 2.&l 2l 1.811 33 0.5 r.434 103 2.582 22 1.778 34 0.5 1.408 11 3 2.524 23 r.738 JJ I I.JYJ 12 10 2.M8 24 1.708 JO r r.Jlt

TasLE 7. Crrnurcer- Awer.vsns or A.DAMTTE

ZnO 56.77 56.78 31 85 49.t| 54.32 54.90 CuO 23.45 r.7s tr CoO 0.52 5.16 FeO 1.48 MnO 0.11 Rare earths 0.39 AszOs 40.09 38.96 39.85 39 24 39.95 39.80 (1 HrO J.l+ ? 3.68 4.25 4.55 3.45 Rem, o.26 0.69

Total 100.00 99.53 100.22 99.51 100.30 99.34 G. 4.435 4.352 4.338 4.319

1. Znz(AsOr)(OH).2. Mapimi, Mexico.McCIean analyst, 1947. Rem. is SiO2.3. Cap Garonne,France (cuprianadamite). Pisani (1870).4. Cap Garonne,France (cobaltian adamite).Damour (1868). 5. Chaflarcillo,Chile. Friedel (1866). 6. Balkhashregion, USSR. Rem. is SiOz.Kukharenko (1939). spectrographic analysis, however, shows that other elements are present in significant amounts: Cu-O.1, Pb-0.1, Fe 0.01-0.1, Mg 0.01-0.1, Al-0.01, Ca-0.01, Ag 0.001-0.01, Ga-0.001. Of the 11 analysesof adamite reported in the literature,l only that of the material from Thasos, Turkey, is comparable in purity to the Ma- pimi . The axial ratio and specificgravity of the crystals from these two localities also are more closely related to each other than to material

I Ten analyses in Doelter (1918); with a more recent analysis by Kukharenko (1939). ADAtr,TITEFROtr,I MAPIMI, MEXrcO 4JJ from other localities. The other reported analyses of adamite all show various amounts of Cu, Co or Fe" in substitutional solid solution, and small amounts of Mn" and rare-earthsalso have been reported. Substitu- tion of P for As has not been reported although this occurs in some re- lated , notably , CaCu(AsOa)(OH).The analyses showing the maximum amounts of these substituting elements so far reported are cited in Table 7, and.the atomic ratios of the cations corre- sponding to these analyses are given below. Sufficient data are not at hand to permit a definitive statement of the relation between

cuprian adamite (analysis 3) Cu: Zn:1:1.33 cobaltian adamite (anal1'5is4) Co:Zn:1:8.8 ferroan adarnite (analysis 5) Fe:Zn:l:32.4 the variation in composition and the concomitant variation in optical properties and specificgravity.

AcruowrBocMENTS The writer wishes to take this opportunity to expressher gratitude to Dr. Clifford Frondel and Dr. C. Wroe Wolfe for valuable suggestions and advice during the preparation of this paper; also to Mr. Dan Mayers and Mr. Francis Wise for material on which this study was made, and for providing the chemical analysis.

Norns oN THE OccunnnNcB The Ojuela Mine is located at the base of the northeast escarpment of the Sierra de Mapimi, about five miles southeast of the town of Mapimi, Durango. It is one of Mexico's largest mines, and one may spend weeks travelling underground without revisiting the same spot. The mine has been worked to shallow depths for rich secondary silver since 1600. In 1893 it was converted into an enormous -silver property by the American Metals Company and almost four million tons of , assaying on the average 3.7 grams gold, 462 grams silver and 14.9 per cent lead have since been mined. Large scaleoperations ceaseda decadeago in the face of mounting drainage difficulties and depletion of reserves,and work is now carried forward by a cooperative. The Ojuela deposit is a limestone replacement, typical of (Hayward ( 1931) and Foshag ( 1934)) . Mineralization is controlled by a system of fractures and favors certain dolomitic horizons. Unlike other similar depositsthe Ojuela Mine showssigns of igneous activity in its lower workings, small pegmatite veins being present. Enormous caves and pipes, widely separated by barren limestone, contain the principal ore bodies. 456 MARY E. MROSE, DAN E. MAYERS AND FRANCIS A. WISE

In general,the mineralogy of the Ojuela Mine resemblesthat of Tintic, Utah; most of the speciesof one locality are representedat the other, al- though copper minerals occur lessabundantly at Ojuela. Primary mineral- ization emplaced extensive sulfide bodies composed chiefly of arsenopy- rite, pyrite, sphalerite and argentiferous galena. , qtattz, fluorite and limonite are the important gangue minerals. A wide variety of minerals resulted from intensive oxidation, among them the arsenates for which the locality is noted. Unfortunately, many of the rarer arse- nates, including , , arseniosiderite,and dussertite have been encountered only sparingly in dump material. A detailed descrip- tion of theseminerals has been given by Foshag (1937). In June, 1946, the writers had the good fortune to discover a remark- able pocket of adamite in a small manway of the Las Palomas ore body, just above the 11th level. Enroute to a stope containing fine specimens of and green mimetite, our lamps fell upon a pocket in the lime- stone. We saw a miniature grotto, somefour feet in diameter and as many deep, its interior carved into fantastic shapes and the entire surface covered with smoothly undulating waves of sparkling yellow crystals; it was a glorious sight, as though we were gazingupon a mineral specimen of unimaginable splendor! Although we could hardly credit our good luck, we set miners to work immediately and obtained some extraordinary specimens.The largest weighed 75 pounds underground, and was almost 3 feet square; it exhibited a continuous crust of green crystals about ] inch in size resting on a matrix of brown limonite. This specimen,after being trimmed in shape, now rests in the U. S. National Museum. Two other notable specimensare contained in the Harvard collection. Crystals of adamite from this pocket range up to 5f I6tt in length. The color varies from water-white through yellow-green (the predominant color) to a pale bluish-yellow. Smaller pockets of adamite subsequently found in the immediate vicinity contain crystals of a paler yellow color. fn addition to the adamite found underground a few specimens were collected from surface dumps near the Norte and America No. 1 shafts. These specimenswere of poor quality but occasionally exhibited a pink- ish color and were sometimes on a matrix of arseniosiderite,while the matrix of the adamite found underground was merely limonite or lime- stone. The particular pocket of adamite which we discovered appears to have resulted from a combination of favorable conditions. It seemslikely that descendingsolutions were -rich, as , occurring in large crystals reminiscent of those found at Santa Eulalia, , is abundant in the Palomas ore body between the 11th and 12th levels; although no hemimorphite was found associatedwith the adamite, smith- ADAMITE FROM MAPIMI, MEXICO lJt sonite was sparingly present. The adamite pocket occurred in an elbow of the Las Palomas ore chimney and solutions entering this pocket would tend to stagnate, permitting undisturbed alteration and the growth of large crystals. RnrBnBNcrs

Arotst, P., Adamina di Monte Valerio (Campiglia Marittima): Ri.t;.di. Miner. e Cri,st., 39, 58-64 (1909). DArtoun, A., Sur un ars6niate de zinc naturel provenant du Cap Garonne (department du Yar)'. Compt. rend.,62, 1124-1129 (1868). Dan-l, E. 5., System o! Mineralogy,6th ed., 786-787, John Wiley & Sons,Inc., New York (18e2). DnsCr.orzneu, A., Adamine du Laurium:Bull. soc. min.,lr 30-31(1878). Donr.tnn, C., Hand.buchder Mi.neral-chemie,3, [1], 695-697 (1918). Fosnec, W. F., Carminite and associatedminerals from Mapimi, Mexico: Am. Mi.neral., 22,47++84 (1937). Fosnec, W. F., The ore deposits of Los Lamentos, Chihuahua, \{exico: Econ. Geol.,29, 330-345(1934). Fnrnoor., C., Sur l'adamine, nouvelle espdcemin6rale: Com.pt.rend,.,621 692-695 (1866). Havwlnl, M. W., alro Tnrnlott, W. H., Occurrence of lead-zinc ores in dolomitic lime- stones in northern Mexico: A.I.M.E. Technical Publication No. M2 (1931). HrNtzr, C., Adamin AsOZ.n(ZnOTJ): Handb. d,erMin., l,14A1,643-649 (1933). Korronos, P., Uber die Struktur von Adamin: Ze,its.Kr,ist.,96,417-435 (1937). Kuru,mrNxo, A , Adamite from the Gulshad Deposit (northwestern Balkash region): M€m. Soe. RusseMi.n.,68, ser. 2, 589-600 (1939). Lecnorx,A.,Adamite: MinEralogied.elaFronceetdesesColonies,4,+24-427(1910). Lrsrovnrs, II., Adamin-Krystalle von Laurium: Zei.ts.Krist.,2, 147-153 (1878). LrNncnnN, W., Mineral Deposits,4th ed, 598, McGraw-Hili Book Co., Inc., New York (1933). Mun-oocn, J., Adamite {rom Chloride Clifi, '. Am. Mineral,.,21, 811-813 (1936). PtseNt, F., Sur les min6raux trouv6s dans la mine de cuivre du Cap Garonne (Var). Ada- mtne: Compt. rend..,7O,1001-1004 (1870). Rrcruoro, W., Cr1'51a16hgmistry of the phosphates,arsenates and vanadates of the type A,XOa(Z): Am. tr'[,ineral.,25, 4J^1479 (1940). Rosrcrf. V.. Adamin von Thasos in der Turkei: Bulleli,n internationatr de I'Acail€mie iles Sciencesde Bohtrne, 1-8 (1908); Zei,ts.Kri.,48, 65G660 (1910). DE ScrrurrnN, A., Reproduction artificielle de la kcettigite et de I'adamine: Bul'l'. soc. min.,26,93-95 (1903). Strrrrs, L., Adamite from Gold Hill, Tooele Co., lJtah: Am. Mineral.,zo, 37l-376 (1935). SrnuNz, H., Vergieichende rcintgenographische und morphologische Untersuchung von Andalusit (AIO)AISiO4, Libethenit (CuOH) CuPOr und Adamin (ZnOH)ZnAsOr: Z eitrs.Kri.st., 94, 60-7 4 (1936). Uncnnecu, H., Sur I'adamite: BuII. soc. rnin., 44, 122-128 (1921) .