Canadion Mineralogist Vol. 30, pp.215-217 (1992) FERRILOTHARMEYERITE.A NEW CA_ZN_FE3*HYDROXVL ARSENATE FROM TSUMEB,NAMIBIA1 H. GARY ANSELL ANDANDREW C. ROBERTS GeologicalSuney of Canado,601 Booth Street,Ottowa, Ontario KIA 0E8 PETE J. DUNN Departmentof Mineral Sciences,Smithsonion Institution, Washington,D,C, 20560,U.S.A, WILLIAM D. BIRCH Deportmentof Mineralogyand Petrology,Museum of Victoria,Melbourne, Victoria 3000, Australia VALERIE E. ANSELL 22 Fairhill Crescent,Nepean, Ontario K2G 187 JOEL D. GRICE Mineral SciencesSection, Canadion Museum of Nature, Ottawa,Ontario KIP 6P4 ABSTRACT Keywords: ferrilotharmeyerite, calcium zinc ferric iron hydroxyl arsenate,new mineral species,X-ray data, Ferrilotharmeyerite occurs at the Tsumeb mine, chemicalcomposition, Tsumeb mine, Namibia. Tsumeb, Namibia, as multiple subhedralcrystallites and as tabular to wedge-or lozenge-shapedcrystals associated SouvernE with tennanXite,scorodite, conichalcite, schneiderh6hnite and beudantite.The mineral is monoclinic, spacegroup A, Cm or A/m (diffraction aspectC*/*), with refinqd La ferrilotharmeyerite,nouvelle espdcemindrale pro- unit-cell parametersa 8.9!!(7), b 6.236(2),c 7.390(3)A, venantde la mine Tsumeb, en Namibie, est pr6sentesous P 115.74(4)',V373.5(5) N, o:b;c1.443:l:1.185, Z = 2. forme de petits cristaux sub-idiomorphesou en tablettes The strongestseven liner of the X-ray powder-diffraction ou en losanges,associds i tennantite,scorodite, conichal- pattern [d_ in ND&k}] _are: 4.95(70)(ll0), cite, schneiderhcihniteet beudantite.Elle est monoclini- 3.398(100X202), 3.175(190)(ll2), 2.93_8(100)(201),que,. groupe spatial c2, cm ou a/m (aspect de 2.823(70)(02r),2.7 02(7 0)(3t r), 2.544(l00tp2l). The crys- diffraction C*l*); les parambtres r6ticglaires ont 6te tallites are transparent to translucent, medium to affi n6s:a 8.227(7), b 6.236(2),c 7.390(3)A\ P | | 5.74(4)", brownish yellow with an adamantineto greasylustre and V373.5(5)N,a:b:c 1.u93:l:1.185,Z = 2.Lesseptraies a paleyellow streak.The mineralis brittle, with an uneven les plus intensesdu clich6 de diffraction (m6thode des fracture and a good [001]-cleavage.D(meas.) 4.25(5), poudres) ld en A(I)(hkl)J sonr: 4.95(70)(110), D(calc,) 4.25 and 4,38 g/cm'for two empirical formulas. 3.398(l@X2@), 3.r75(l00X1la, 2.938(100)(201), Optically,the mineralis.biaxial positive, with o 1.811(5), 2.823(70)(02r),2.702(70)(311),2.su(r0o)Q21).Lespetits B 1.844(5), r I .88(l), 2V(meas.)85(5)', 2 Z(calc.) 89", X cristaux sont transparentsir translucides,jaune moyen ir y approximatelyIl o, | | b. Pleochroismis strong: X jaune brunitre, avec un 6clat adamantin ou glas et une olive green, Y pale green, Z colorless.Absorption is X rayure jaune pdle. C'est un min6ral cassant dont la > f >> Z. lnclined dispersion of the optic axes is lracture est irr€gulidre; le clivage [001] est bon. Densit6 distinct, r > v. The ideal chemical formula is 4.25(5)(mesur6e),4.25 et 4.38 (valeurscalcul6es pour les Ca(Zn,Cu)(Fe3+,Zn)(AsO3OH)z(OH)s,derived from deux formulesempiriques). Biaxe positif, aveco l.8l l(5), electron-microprobeanalyses, water determination and p 1.844(5),y 1.88(l),2Z(mes.) 85(5)",2V(calc.) 89", X microchemicaltests. Ferrilotharmeyerite is the ferric iron y i peu prds ll a, I I b. Le pl6ochroismeest intense: X analogueof lotharmeyerite,and is named to reflect this vert dlive, Yvert pAle,Z incolore. L'absorption est X > relationship. Y >> Z. La dispersion inclinde des axes optiques est distincte, | ^> v. La formule chimique id6ale, Ca(Zn,CuXFe'*,Zn)(AsO3OH)z(OH):, est ddriv6e de donn€es obtenues ir la microsonde des rGeological dlectronique, Survey of Canada contribution number d6terminations de la teneur en H2O, et de tests 15690. rnicrochimiques. Le ferrilotharmeyerite est I'analogue 225 226 THE CANADIAN MINERALOGIST ferrifdrede la lotharmeyerite,et son nom t6moignede 7.38 A, I115.57', Thesedata are consistentwith cetterelation. those reported for lotharmeyeriteby Kampf et al. (1984).Because upperJevel precession photography (Traduitpar la R6daction) was impossibleand the X-ray powder patterns of Mots-cl6s:ferrilotharmeyerite, arsenate de calcium,zinc, the two mineralsare very similar, it was decidedto fer ferrique hydroxyl6,nouvelle espbce min€rale, index the powder pattern of ferrilotharmeyeriteby donndesaux rayonsX, compositionchimique, mine analogy with the powder data provided for deTsumeb, Namibie. lotharmeyeriteby Kampf et ql. (1984).Ferrilothar- meyerite crystals from specimenM38092 are also INTRoDUCTIoN unsuitable for single-crystalprecession study. The X-ray powder-diffraction data for specimen A new mineral, ferrilotharmeyerite, has been NMC 64573 (Table 1) were refined qsing twelve identified on a specimen (NMC 64573) in the reflectionsbetween 3.5M and 1.559 A for which National Mineral Collection of the Geological unambiguousindexing was possible. The refined Survey of Canada. The sample was collected in unit-cellparameters are:. a 8.997(7),b 6.?36Q),c 1983by John Innes, from the Tsumebmine (32 7.390(3)i\ I ttS.lq@)', V 373.5(5)N, a:b:c level, W40 stope), Tsumeb, Namibia. The mineral 1.443:l:1.185,with Z : 2. The'possiblespace- occursas multiple subhedralcrystallites, averaging groups, also by analogy, are C2, Cm or C2/m 0.2 mm in length, with crudelyformed facesslightly (diffraction aspectC'r'lx'). The cell parametersand elongatein the b direction. The matrix appearsto cell volume are slightly lower than those reported be feldspathicquartzite showingpervasive staining by Kampf et al. (1984) for lotharmeyerite. Con- by hematite. Ferrilotharmeyeriterims conichalcite tributing factors for the smaller unit cell are the and is in contact with tennantite. Large crystalsof small but significant- differences in ieni! radii scorodite and schneiderhdhnitealso occur on the berweenFe3* (0.64 g) and Mn3* (0.66^A), and specimen. berweenCu2* (0.72 A) and zn2^ (0.74 A). After most of the data needed to define the specieshad been obtained on the NMC specimen, PHYSICAL AND OPTICAL PROPERTIES additional ferrilotharmeyerite from the same locality was found on a specimen of massive tennantite and calcite from the Museum of Ferrilotharmeyerite on specimen NMC 64573 Victoria, Melbourne, Australia (M38092). This occursas subhedralcrystals, averaging 0.2 mm in specimenhas a 7 x 7 cm crust of dark brown TABLE I. X.RAY POWDER DATA FOR TERRIII'TIIARMTIERIIts tabular beudantitecrystals up to I mm across,and yellowish brown ferrilotharmeyeritecrystals up to /est. d(tu6.) d(elc.) hH /sL d(m6) l(€lc) hkl about 0.6 mm in size. The water analysis for ferrilotharmeyerite was obtained from this 30 6.66 6.66 001 5 L010 2'069 311 specimenbecause of the dearth of material on the 70 4.95 494 110 5 LV6 LM6 400 NMC specimen. 30 4.60 4.59 trT , 1.988 ri s r.983 'I The mineral is the ferric iron analogue of 10 4,44 4.42 zu 1.986 403 _; lotharmeyerite(Dunn 1983,Kampf et al. 1984)and 20 3544 3544 tt1 5 1.9X 1,E24 is named to reflect this relationship. The mineral 100 3398 3395 z6 . 1.850 30 1.U7 |'rs47 and mineral name have been approved by the 100 3.175 3.t'78 ttz M Commissionon New Minerals and Mineral Names. m 3.118 0m , tar2 tn 20 r.8ll I' I.M.A. The two specimensdescribed above have 100 2.938 L940 ml 1t08 u23 been designatedcotype, and are the only known '10 2.92i 2.p4 al rc 1n3 1J7Z D, specimensof ferrilotharmeyerite. 70 2.74 2.7V :ri ' l72l tra 50 1.701 '1.7m| ..; lm 2544 2541 /21 , 2.414 1\2 1"-" 6At 312 X-RAY CRYSTALLoGRAPHY 50 2.475 | so ten [ '2.471 /20 ' 1.675 423 t0 2297 2.296 m 20 1J89 1589 24 Precessionstudies were undertaken on several , zn6 972 30 1J59 1J59 040 fragments r0 2.26 | of ferrilotharmeyerite0.1 to 0.2 mm in '2260 rrl . 1J19 42r. 20 1518 '| size from NMC 64573,but in all casesorientation , 2.2t9 003 1509 r0 2210 | - photographs indicate that single-crystalmultiple '2204 402 . 1.469 23 30 1.468 |'1-468 crystallitesare present.Even the smallestfragment .2.154 2A ffi 20 2.147 | is composedof at leastfour individuals. Neverthe- , 2.139 Z2l less,lr0land b" L20l' photographsofonefragment clearly show monoclinic symmetry and gave - I 14.6 m Debye-schere! powder @e&, Gr adiadotr Ni-filter (lGttro 1J4178 A) - in@miti6 estimatedvisually, valu6 of^d quoted h A measuredunit-cell parameters:o 8.98, b 6.23, c - indsed with a 8.99'7,b 6136,c'1390 A-B 115.74" FERRILOTHARMEYERITEFROM TSUMEB 227 size,in randomly orientedto subparallelaggregates bourne, Australia, provided the water analysisby up to 3 mm in maximum dimension. The crystals CHN Analyzer. Microchemicaltests were negative are transparent, medium yellow to brownish for Fe2+and positivefor Fe3*. yellow, with an adamantinelustre and a very pale The empirical formula for NMC 64573,on the yellow streak. For M38092,the ferrilotharmeyerite basis of As 2, is Cat.x5(Zn6.62Cuo.rr)rr.oo crystals are tabular to wedge- or lozenge-shaped, (Fe6.s7Zn6.1a)s1.61[AsO3.1e(OH)0.e0]2(OH)2.80.The averageabout 0.6 mm in size, and are commonly empirical formula for M38092, on the basisof As intergrown with beudantite. These crystals are 2, is (Ca6.e2Pbs.65)p6.er(2n6.66Cu6.3a)p1.* translucent,with a greasylustre and a pale yellow (Fe6.332n6.154.le.er)gq.eIAsO:.ar (OH)o.ss]z(OH)r.s0. streak. The mineral is brittle, with an uneven By analogy with lotharmeyerite, the idealized fracture and a good {001} cleavage.The Mohs formula is Ca(Zn,Cu)(Fe3",ZnXAsojoH)2(oH)3.