Cana dian M ineralo gis t, Vol. lN pp.262-2f8 (1974)

INFRARED SPECTROSCOPICINVEgTIGATION OF THE STRUCTUREOF SOME NATURAT ARSENATESAND THE NATURE OF H-BONDS IN THEIR STRUCTURES

V. I. SUMIN or PORTILLA Conseio de RecrtrsosNafurales no Renouabla Nihos Heroesg Dr. Nauarro,M*ico D.F., Madqw

ABsrrAcr to t 2 cm-1 in the 400-2000cm-1 region and The IR-spectra of the arsenates durangite, mime- to i 5 cm-l in the 2000-3800 cm-1 region. tite, conichalcitg austinitg olivenite and adamite cor- Deuteration of the samples was carried out by roborate the character of the symmetry of the arsenate means ol a hermetic oven (Nasedkin 1962). Of groups in thce minerals. The changes in the sym- the minerals studied, the only one completely metry of the point group of the anion (AsOn;s- It deuteratedwas conichalcite and the substitution the result of a coordinative bond with metal atoms. took about 20 hours. The hydroxyl group in conichalcitg austinite, olivenite All the minerals investigatedare of the isolated and adamite is linked through H-bonds and coordi- nated with metal atoms. The frequencies of stretching tetrahedron type. Two, druangite and mimetite, vibrations of the hydroxyl group indicate that there have almost regular tetrahedrons and lack hy- are H-bonds with variable strengths between the OH droxyl groups; the others (conichalcitg austinite, groups and the oxygen in the O-AsO3 groups. The olivenite, and adamite) possesshydroxyl groups strength of the H-bond falls in the following order : and their tetrahedral (AsOr) a- structure is some- conichalcite > austinit€ > olivenite ) adamite. what deformed. In the minerals investigated, A band at 740 crn-t in the spectra of Zn-bearing three kinds of interactions are e)rpected: 1) minerals such as adamite and austinite indicates thar donor-acceptor,2) H-bond and 3) electrostatic. the oxygen group partly atom of tlre arsenate is The strongest type of interaction is probably the ptotonated by the hydrogen atom of the OH group. This confirms that there is interaction betwen the the donor-acceptor one, because most of the anion and the cation (coordination) and that OAs metallic cations are capable of forming strong (OH) groups may exist in the structure. The absence complexes and because the anions are strong of bands in the 1500-1700cm-r region mnfirms the electrodonors.These interactions result in changes absence of water molecules in t"heseminerals. in the structure and in t}le chemical bonds and The following structural formulae are proposed : consequently the IR-spectra of these minerals conichalcite, Ca(CuOtI) (AsOa) ; austinite, Ca(Zn are different from the spectra of free arsenates OH)(AsO4) ; olivenite, Cu(CuOlI)(AsOa) ; and and free OH groups. adamitg Zn(ZnOH) (AsOa). According to Mayanlz (1960) and Siebert (1953, 1954, 1966), the tetrahe&al qrmmetry, Imroouc:row 7a, of the arsenateion is indicated by four ab- Durangite, NaAl(AsOa)F, mimetitg Pbs sorption bands of which only two appear in the (fuO4)icl, adamite, Znz(AsO*)OH, olivenite, IR-spectra and have the theoretical values Cu2(AsOa)OH, conichalcite, CaCu(AsOa)OH vr(F2) : 887 cm-1 and ,tE(F) :463 cm-1. and austinite, CaZn(AsOa)OH have scarcely The four bands appear in Raman spectra (Gupta been studied by IR-spectroscopy. Adler (1961) 1948). When coordination of the arsenate ion and Moenke (1962) include the lR-spectra of with metals occurs, as in donor-acceptor bonds, some of these minerals, but they do not discuss then the sJrmmetry of the arsenate group falls them in detail and the spectra are used mainly from C,(Cg,) to C"o (Fig. 1). A redistribution for mineral identification. As r-rav data are available for this group of minerali, their IR- spectra, stmctures, and the nature of their chemi- cal bonds may be correlated and analyzed. 1?1 A1l samples that were used were identified by Ys optical methods and by r-ray analysis. The IR.- 4,& ^" 'Jr(At) 'le (El rlr( Fe) 'J.( F2l spectra registered were with an lR-spectrophoto. Js(XY) dc(Ym Jd(xyl 8a(yxyf meter (Zeiss, GDR) in the 400-3800 cm-l re- Flg. I gion. The samples were prepard. as emulsions Frc. 1. Forms of vibration for the (Asor;s- ,uo.- in nuiol. The spectra remrded were reproducible hedral group. 262

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of the electronic cloud octurs which raises the hedron, giving this mineral a Go sfrnmetry. sfength of some of the fu-O bonds, and de. This agreeswith the correlation scheme (Table creases the strength of other bonds. This also 1) and with the x-ray data. The arrangement results in the formation of new metal-orygen in the correlation table enables one to find the bonds. The lR-spectra permit us to follorv these symmetry of the ligand in the structure of the changes and to interpret their nature. Alt the minerals (Nakamoto 1966). The interatomic symmetry bands vr(Ar) and vr(E) are present. distancesare Pb-Cl : 3.16A and Pb-O: 2.564, As the degeneracy of the vg(Fz) and va(Fz) which are bigger than the sums of the ionic radii bands disappears,these split into two or tlree (2.654 and 2.164), and this fact indicates that componentsand the band of valency vibrations the Pb-O bond is mainly ionic. The ionic nature of the Me-O (Me : metal) bond appears.Other of the Pb-O and Pb-Cl bands is also confirmed bands related to the metal-arsenatesystem also by the absence of absorption bands in the 500- appear.The coordination of the hydroxyl groups 600 cm-1 region where the bands of stretching causes sharp changes in the IR-spectra. New vibrations of the Me-O bonds usually appear. bands related to deformation vibrations of the The IR-spectra of mimetite from Tsumeb, Me-OH bands appear in the 600-1200 cm-1 which has only traces of phosphate, show four region and bands related to stretching vibrations bands of medium intensity in the region of appear in the (Youxnevitch 300-900cm-l region valency vibrations of the phosphate group, that 1963,1970). is in the ,ta(Fz) region. These bands dr€ vga: 960 cm-l, lrab: 990 cm-1, lrac: 1010 cm-1 MrMsrrrE and a weak band vr(Ar) : 925 cm-r (Table 2). Mimetite, Pbo(AsOa)gCl, is an analogue of In the region of deformational vibrations, the apatite and is hexagonal,bipyramidal, 6/m, The v+(Fz) band is split in tlree bands: ! : 545 unit cell has lwo Pbo(AsOa)aClunits (Hendri&s Ctrl*1, i46 : 555 cm-r and Vac: 570 cm-l. 1932; Machatski 1950). The As forms a regular This kind of splitting indicates that the site- tetrahedron with four oxygen atoms, in which sfmmetry of the (POa)u- group in the correla- the As-O distance is 1.94. The tetrahedra are tion scheme must correspond to Cro symmetry, interlinked by Pb atoms. The Pb qtoms in the that is, to a symmetry lower than that of the octahedraresemble empty cylinders on the walls (AsOa)3- groups. of which are the Pb atoms, parallel to the c The IR-spectra of mimetite from Cumberland axis the Cl atoms are ; distributed directlv on show an intense band va(Fz) due to the phos- the c axis. Pb forms a continuous column in phate anion. A weak band at 1320 cm-1 is which each Pb atom coordinates g with oxygens. probably due to an overtone 2 va(POn)3- and These columns are linked together by the (AsO!)f- &trahedra. We studied two samplesof mimetite, one from tumeb, S.W. Afoica, with 1.93% PzOs and an- other from Cumberland, England, with lI/6 PzOs. The lR-spectra of both samples (Fig. 2) show a slight splitting in the region of stretching vibrations of the AsOa groups,that is, the vs(Fz) band. This splitting gives rise to two bands at 790 cm-1 and 820 cm-1. The vr(Ar) band appearsas a weak shoulder at 735 cm-1. In the region of deformation vibrations of the arsenate ion there is a weak splitting of the va(Fz) band into two bands at 415 cm-1 and 430 cm-1. From the lR-spectral data we conclude that there is a slight deformation of the (fuOa)s- tetra- TABLEI. CORRELATIONTABLE FOR GROUPS OF LOCALSYMI'IETRY IN TETMHEDMLANl0Ns (Nakamoto 1966)

ta

Frc. 2. Infrared spectra of mimetite and durangite: cz"ilil;'$ectfa (a) mimetite from Cumberlan4 England: (c) durangite from Durango, Mexico.

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the 1650cm-1 band may be related to the over- cies of the fu-O vibrations are 100 cm-1 higher tone 2 v(AsOn;s-. than in mimetite (Table 2). The lR-spectra of durangite are considerably more complex than the spectra of mimetite (Fig. 2). In the region Dunalrcrrr of valency frequencie vs(F2), a very weak split- Durangite, NaAl(AsOa)R is a rare mineral. ting is observed and it gives the bands rlso: Its structure (Kokkoros 1938) is monoclinig 2/m" 860 cm-l and vga: 915 cm-1. In the v.(Ar) spacegroup Czn, Z: 4. The coordination num- region there is a shoulder at 790 cm-1. In the ber for Na is 7 and for A1, 6. The structure is va(Fe) region that corresponds to deformation ',t+a:4l5 of a sublayer type and is analogous to those of vibrations, two bands are observedi :450 titanite and tilasite (Strunz 1938). In durangite, cm-l and i,6 cm-1. This kind of split- As forms a practically regular tetrahedron with ting clearly points to a deformation in the fu-O: 1.684 in the (fuOa)s- anion.The atoms (AsOa)s- groups giving a C . s,ymmetry, which ol Al are surrounded by four oxygen atoms and is in agreement with the correlation table and by two F atoms that form an octahedral struc- the r-ray data of Kokkoros (1938). ture, AlOaF2, in which the interatomic distances The lR-spectra of mimetite, which is a typical are: Al-O : 1.81-1.904and Al-F: 1.814. In ionic compound, clearly differ from the spectra the vicinily of the Na atoms there are six O of durangite, which is a mineral with coordina- atoms and an F atom, with interatomic dis- tion bonds. For durangite, the two bands.at 525 ta.nces:Na-O : 2.40-2,474and Na-F: 2.354. cm-1 and 560 cm-1 are probably due to anti- These form NaOoF polyhedra. symmetrical stretching vibrations of the Al-F and A1-O bonds in the octahedra. These two values A fundamental difference between mimetite are in the region of vibrational frequencies for and durangite is the presence of Al atoms in the AlOo group (Nakamoto 1966). The observed durangite that are capable of forming strong spectral splitting may be explained as the result covalent bonds. This is corroboratedbv the fact of a slight deformation in the symrnetry of the that the A1-O interatomicdistances (l.bl-1.90A) octahedra.In durangite the 1030crn-l and 1098 are simificantlv lower than sum of the ionic 'ihe cm-l bands are probirbly due to the 2vA1-F and radii [.93A). coordination of the Al atoms 2vAl-O overtones,and the 1650 cm-1 band is with the arsenate groups in the structure of also probably due to an overtone 2vs(AsOaX-. durangite decreasesthe As-O interatomic distance It is concluded that the increaseof the vs(Fz) to 1.634 as compared 1.824 in mimetite, thus value by 100 cm-1 and the appearance of a indicating that the As-O bond in durangite is 560 cm-1 band related to Al-O bonds are a the stronger. characteristic of coordination between arsenate The change in the energy of the valency bonds groups and Al atoms. Therefore, it is possible to leads to changesin the IR-spectra.The frequen- clasbify durangite as a compound with strong

TABLE2. INFRAREDABSORPTION BAND FREQUENCIES. ( lAs P)oal3- 0ll..0

MJneral v1(/1) u3tozJ uo(12) Fd:O---T-d E -n----T-:O 6sn--7:6; '(ua-o) 60HvOH v(0H..0) 2t cm zv4\vud- t5zu PbUlAs0nlrcl 820 990 430 555 -1650 t010 570 ?v3(AsOn) Duranqite 830* 415 525(Al-F) Zv(Al-F) l03U NaAl[Asoo]F 450 560 2v(Al-0) i0e8 3f3_ 2vr(AsOn)l650 '1040 0l ivenite 750* 800 '1090 400 545 950 3440 3050 CurlAsOnJ0H 830 452 870 Znr[AsOnJoH 830 485 535 m9 CaCuIAs0n]0H 820 430 !q?q(?qqg) ?Zgq 2v(As04)1650 840 460 1060 3170 2730 (815)(2360)

CaZnIAs0OJ0H 430 s70 980 3300 465 l0l0 t shoulder ( ) frequencies of absorption bandsof deuterated samples

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covalent bonds and mimetite as a compoundwith The IR-spectra of conichalcite (Fig. 3a, Table bonds of an ionic nature. 2) show a band splitting in the vs(Fz) region of vibrational frequencies of arsenate groups. The : Corrrcrrercrrn axp Ausnryrrg splitting gives four bands: vso 795 cm-1, vea: 820 cm-1, vac: 840 cm-1, and vsa : The structure of austinite is not known, but 865 cm-l. The v:.(Ar) band is observed as a as austinite and conichalcite are isomorphous. weak shoulder at 740 crn-l. The region of de- their structuresmust be of the r"*" typ". Both formation vibrations, ,t+(Fz), has three well-re- minerals are basic arsenates with isolated solved bands "ia6: 410 cm-1, 1l+b: 430 cm.-l, (fuOo;*- groups in their structures.Their unit and va": 460 cm-1. According to the correla- cell is orthorhombic with 4[CaCu(A:O*)OH] in tion table (Table 1), the arsenate anion has a conichalcite and 4[CaZn(fuOr) OH] in austinite. C2, symmetry, which agreeswith the x-ray data The conichalcite structure has been investigated by Strunz (1939) and Qurashi et al. (1953,I9il, 1963). The lattice of these two minerals consisrs TABT.E3. X-MY DATAOF SOMEARSENATES }lI]H ISOLATEDITTRA}IEDM of deformed (AsOo;s- tetrahedra. Each Cu (or Mineral Ion o(r) o(z) o(g) o(q) 015;/oHSrretrY Zn) atom is surrounded by an octahedron of o)iygen atoms, two of which belong to -OH !tE cu 2.09 2.38 2.?8 1.95 groups and four to the arsenate group. Each Ca 2.O4 *f ca 2.54 2.68 ,t1 2.51 2.36 atom has eight neighbouring atoms. Seven are 2.48 2.46 ?.54 .:= nH 2,74 oxygen atoms belonging to arsenate groups and 2.90 3.18 2,97 the eighth is an oxygen atom or a hydroryl 2.97 3.04 group. The interatomic As 1,49 I .45 t .8l L8l distances are given in cu(t 2.12 2.34 2.34 t06 Table 3. ) 't.96 Cu,^\ 2.03 I .99 The sample of conichalcite that we used is \') 2.16 t.gz 1.92 from the Lachin-Han deposits, Uzbekhistan, and orf 2,97 2,78 2.85 2.85 was provided by the Mineralogical Museum of I.59 I.59 1.81 I.8t 3.01 Deformed '1.99 tetrahedron the Academy of Sciences of the USSR (No. Znr,t 1.84 t.84 r.9t 2.19 Trigonal M923). The Lachin-Han deposits and conichal- blpyranid cite have been tJroroughly znt"t 2.O8 2.29 2.29 2.0S described by Dunin 2.08 i e.08 (re62). 0H 2.8 3.03 2.79 3.04 2.86

Frc. 3. _Infr-ared spectra of conichalcite and austinite : (a) conichalcite from Laclin-han, USSR; (b) deuterated coni&alcite from fa*rin-lan; (c) austinite from Hovon-alai, USSR; (d) austinite from Ojue'4 Mexico. For ctq-l? read crn-l.

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(Qurashi et aI. 1963). A band of high intensity (Yahontova 1968). The Mapimi austlnite has at 575 cm-l is attributed to the stretchingvibra- not been ihemically anal1zed. tions of the Cu-O bonds becausethe band does The IR-spectra of both samples are very simi- not change after deuteration of the mineral. The lar'. In the vs(Fz) region, two bands were ob' presenceof Cu-O bonds is corroborated by x-ray served at 845 cm-1 and 800 crn-1. The vt(Ar) data on the coordination of arsenate groups with band is poorly resolved and appears as a shoulder Cu atoms. The interatomic distances of 2.M- at 750 cm-l. In the vc(Fz) region bands appear 2.284 ior the Cu-O bond are significantly less at 410 cm-l, 430 cm-1 and a sharp shoulder at than t}.e sum of the ionic radii, which is about 465 cm-1. This splitting (Fie. 3), according to 2.344 (Qurashi et aI. 1963). The 3480 cm-l the correlation table (Table l), is probably band is due to vibrations of the hy&oxyl groups, linked to the site-qfmmetry of the arsenate ion. which also give absorption bands at 3170 cm-1, The arsenate grotrrp in austinite is probably less 1060cm-1, and 930 crn-1. The relation of these deformed than in conichalcite. This may be due bands with the hydroxyl groups is based on their to the specific crystallochemical properties of Zn shift after deuteration with D2O (Fig. 3b). The that takes, in austinite, the place that Cu has in spectraof deuteratedconichalcite has the follow- conichalcite. ing features: The 525 crn-1 band is related to stretching l. The 3170 crn-1 band is displacedto a lower vibrations of the Zn-O bonds. The Mapimi frequency region and appears as two sharp, strong austinite shows a weak band at 570 cm-1 which bands at 2360 cm-l and 2380 cm-1. The coeffi- is analogousto the band of stretching vibrations cient of isotopical shift is given by: OH 3170/ of Cu-O bonds in conichalcite; this band is OD 2370 = 1.33. probably due to tJre presence of traces of Cu in Z The intensity of the 930 cm-1 band is the austinite from Mapimi. The 915 cm-l and lowered and the band shifu to a lower frequency 980 cm-l bands are due to deformation vibra- (695 crn-t;. The shift also reveals a previously tions MeO-H. hidden band at 960 cm-1. The coelficient of In the spectra of samples from Hovon-alsi isotopical shift is given by: vOH 930/vOD 695 (Fig. 3c), the region of valency vibrations of OH = 1.33 groups shows a sharp symmetrical band at 3300 3. The intensity of the 1060cm-1 band is also cm-1 and a poorly-resolved wide band which lowered and its displacement reveals another appears as a shoulder at 3350 cm-l. The IR- band at 1020 cm-l. Taking into consideration spectra of austinite from Mapimi show an asym- the coefficient of isotopical shifu the 1060 cm-x metrical band at 3X0 cm-L and a shoulder at band should be displacedto 750 cm-1. Observa- 3520 cm-1, which are due to the presenceof tion of the displaced band is obscured in this H-bonds of different strength. This difference in reglon by the stretching vibrations band vr(Ar) strength of the H-bonds is probably linled to of arsenate groups. differences in the cationic composition of the 4. The M80 cm-1 band is probably shifted to two samples. (The 1400 cm-1 band in the IR- 2600 cm-1 where a wide absorptionband appears spectra of austinite from Mapimi indicates the in the spectra of the deuterated samples. presence of carbonate that is probably a me- chanical contamination) . The 3170 cm-x band in the IR-spectra of frequencies of the stretching vibrations conichalcite is related to the stretching vibra- As the groups in conichalcite (3170 tions of the OH groups in arsenates.These hy- of the hydroxyl cm-1) a.re lower than in austinite (3270 cm-t droxyl groups are linked, tlrough strong H- 3300 cm-r), the H-bonds are stronger and bonds, with the oxyjen of arsenate groups. In and than in austinite. From fact the oxygen atoms of the arsenate groups shorter in conichalcite the of IR-spectra and r-ray data the the strongest acceptors for H-bonds in the min- comparison hydroryl groups are coordinated eral. The x-ray data (Qurashi ef ol. 1963) show arsenate and Zn and Cu. We can thus consider cpni- that the lowest value for the O(s) ... (HO) with and austinite as minerals with coordi- distance is 2.744, in agreementwith the inter- chalcite we propose the formulae atomic distance in a strong H-bond. The wide nation bonds and (ArO, for conichalcite and Ca band at 3480 cm-1 is probably due to weaker Ca(CuOH) (ZnOH) (AsOe) for austinite. H-bonds as is indicated by the higher interatomic distances (2.90-2964) between oxygen atoms. awo Aoamrtr Two samples of austinite were used, one from Or.rw;lnrs Mapimi, Mexico and the other from Hovon-aski, These minerals were included becausethey are Touva, USSR. The latter contains Me Q.5%), typical arsenates of the isolated (fuOe) group Mn (L.6%) and Co and Ni (less than l%) type and contain hydroxyl.

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The adamite sample is from the ojuela de. atom are linked by a common edge.The chains po;its, Vlapimi, Mexico. The mineralogical, opti- are interlinked by the Cu bipyramids and the cal and chemical propertiesof adamite have been (fuOr)u- tetrahedra. stydi-edin detail by Mrose (1943). The sample The structure of adamite is analogous to the of olivenite is from Tsumeb, Ahica, and ias structure of olivenite except that the Zn atoms obtained from the Mineralogicat tvturuu* of n. occupy Cu positions. Interatomic distances for Academy of Sciencesof the USSR. This mineral these two minerals are given in Table 3. has also been thoroughly described (Richmond The lR-spectra of our samples showed a band 1940; Berry 1951). vs(Fz) split into four components (Fig. 4). The .-A4ryUte Znz(Asoe)oH, and olivenire, cuz vt(Ar) band is not completely resolved and has (ASO4)OH, are orthorhombic and isostructural. the form of a shoulder at 740-750 cm-1. Two The structure of adamite has been described by intense bands appear in the ve(Fz) region. It is Ko,kkoros(1937) and that of olivenite by Heritsch probable that the third component of the ya(F2) (1938). Both minerals have a deeply'deformed band is located in a lower frequency regton, tetrahedron (AsOn;u- as the basis of tleir struc- beyond the 400 cm-1 limit that we could regis- ture. The tetrahedra have interatomic fu-O dis- ter. From these data we conclude that the sym- tancesof 1.49-1.314in olivenite and l.5g-l.8lA metry of the (fuOa)3- group is lowered to C, or in adamite. Half of the Cu atoms in olivenite Czo {td this concurs with the x-ray data. The have an octahedralcoordination typical of Cur+ ; deformation of the tetrahedron may be explained two o,xy-genatoms and two hydroxyl groups flrr- by the linking of the arsenategroup with an atom round the Cu ion, formins a square with Cu-O of Cu or Zn tlvougb cpordination bonds. This interatomic distances of 2-.03A ?or the hvdroxvl supposition is confirmed by the presence,in olive- (Cu-OH), and 2.L2-2.M.for the oxygen-in the nite, of a stretching vibration band of Cu-O at arsenate(Cu-OAsOs). The two remaining orygen 545 cm-1, which can be observed after deutera- atoms_are at a larger distance from the Cu atom tion. The splitting of this band in adamitg which (2.394). Their coordination polyhedra have the gives two components at 515 qn-l and at 585 geometry of a deformed trigonal bipyramid which cm-l for the valency vibration band of Zn-O, has five olrgen atoms and one hydroxyl group indicates that its octahedra have a lower sym- on the apices. The Cu atom is slishtlv shifted mefry. from the center of this biplr.amid and has a The presence of deformation vibration bands medium Cu-O distanceof 2.034 for the hvdroxvl Me-OH in the 900-950cm-1 region confirms the (Cu-OH). The oxygen octahedraaround thu i" coordination of the hydroxyl group with the

s 16 !@ e@ t& B6 t!@ ra6 r?@ t!@ reoto !@

Fic.- 4. Infrared spectra of (a) olivenite from Tsrmreb, Africq and (b) adamite from Ojuela, Mexico,

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atom of metal. This agreeswith the shift of the (1938) : Die Struktur des Olivenites Cu2 950 cm-1 band after deuteration of conichalcite. (OH) (AsO4). Z. Krist. 99' 66-479. Adamin. Two sharp bands of equal intensity at lMO Kogonos, P. (1937) : llber die Struktur von 1090-1 may be due to the Z. KrLst.96, 417- cm-1 and at ls(Fz) (1938): Uber die Struktur der Durangit phosphate vibrations of the anion. Chemical NaAl(AsOrF. Z. Krist.99, 38-49. analysis of the Tsumeb olivenite gave 1.5/6 Mecr+artrq F. (1950) : Kristallchemirche Notizen. phosphorous. Tschemnks Mineral. Petrogr. Mitt. 3, Bd. 1, 424' The absenceof absorption bands in the 1500- ai. 1700 cm-1 region shows that neither olivenite Mavaxz, L.S. (1960) : Theorg and Calculntion of nor adamite contains water. The 34/.:0 cm-l Vibratians of Molecula. Acad. Nauk. SSSR band in olivenite correspondsto the stretching Mouvrr, H. (1962) z Spectralnn'aliseuon Mineralien vibrations of the hydroxyl groups.The high value und Gesteinen. I*iwig 1962. Mar;rrns, D,E. & Wrsn, F.A. (1948) : of the band at 3580 sn-1 in the spectra of Mnosr, M,E., from Ojuela Mine Mapimi, Mexico. groups show Adamite the adamite shows that its hy&oxyl Amer. Mineral. 33' 449-457. less indication of hydrogen bonding than those Nareuoro, K (1966) ; Infrared Spectra d lrnrga'nic in olivenite and therefore interatomic distances and Coordinatbn Compounds. (Russ. ed.) Moscow between oxygen atoms O-----H-O should be 1vllr. larger (Table 3). X-ray data corroboratethis. Qunasnr, M.M. & Bannrs, V/.FI. (1963) : The struc- From the combination of. x-ray and infrared ture of mnichalcite. Con. Mineral. 7' 561-577. data, it is concluded that the arsenateand hy- & _ (1954) : The structures of droryl groups are coordinated with the Zn or Cu the minerals of the descloizite and adelite groups : (part l), Amer. atoms. The hydroxyl groups form H-bonds with l.-Descloizite and conichalcite Mineral. 39' 416-435. a varying degree of strength and when coordina- & Bnnnr, L.G. (1953) : The tion occurs, they bind through H-bonds. It is space group of conichalcite. Amer. Mineral. 3E, considered that the formulae of adamite and 557-559. olivenite should be representedas Cu(CuOH) fucrrvrom, W.E. (1940) : Crystal cheuristry of the (AsOa) and Zn(ZnO}l; (tuOa) respectively. phosphates, arsenates and vanadates of the type A2XO4(Z). Amer. Mineral. 25' 441479. SrrnBnr, ff (1953) : Uber die Verwendung der mole- AcrNowr.soclvrEl.trs kularen Kraftkonstanten zu strukturchemischen Au- The author is grateful to Professor G. P. Bar- sagen. Z. Anorg. allg. Chem. 2i13, 170-182. zanov and Dr. B. E. Zaitsetr for their help in (1954) : Struktur der Saurstoffsawen Z, this studn which formed part of a Ph.D. Thesis Anorg. aIIg. Chem. 275, 225-24A. (1966) : Anwendmgm der Schwingmgs at Moscow University. Spektroskopi.ein d.er anorganishen CheftLie. Springer- Verlag, New York RrnrruNcss Srnurvz, H. (1938) : Isomorphie zwischen Tilasit' Durangit und Cryophiolit. ZbI. Min. GeoI. PaIe' Aornn, H.H. (1961): Infrared spectra of phosphate ' in aont., Abl A 2, 59-60. minerals: Sp:rmetry and substitutional effects (1939) : Mineralien der Descloizit-gruppe: pyromorphiteseries. Amer. Mineral. 49, 1002- tlre Konichalci! Stashiciq Austinit, Duftit, Araoxen, Vol- 1015. z. Krbt. 101(A), 496-506. (1951) mnichalcite, borrhig Pyrobelonit. Brnr.v, L.G. : Observationson L.K. & Sror.anovt, T.A (1968) : A and olivenite. Yaerox'rova, comwallitg euchroite, liromnite of austinite. DokI. Aka& /Vaulc. SSSR 181n 36 484503. sample Amer. Mineral. 1227-1228. Durvnrr-BanrovsraveE't (1962): Conichalcite and Youcnrvsvrrcr, G.V. (1963) : Advances in the appli- stashicitefrom Lachinhan,Zap. Vses.rein Obsh. cation of lR-spectroscopy to the study of H-Bonds. 91,146-148. tlspehii Hgnii 32, 1367-1423. Ilervonrcrs, S.8., Jrrr"rnsow, M.E. & Mos-nr, VM. (1970) : Application of lR-spectmscopy (1932) and : The crystal structuresof somenatural study of water in minerals. C,ollection" Z. Krist. 81r 352- for the synthetic apatite-like substances. Bound Water in Dispersed. Sysfem:. M.G.U. 369. (Moscow University). Hrnrrscr, H. (1937): Vorbericht iiber nintgenogra- phische Untersuchungen an Olivenit Cu2(OH) Manuscript receiuedAu*$t IW3, emended Nouember (AsOr). Z. Krist.98, 351-353. rw3.

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