Brianyoungite, a New Mineral Related to Hydrozincite, from the North of England Orefield

Brianyoungite, a new mineral related to hydrozincite, from the north of England orefield

A. LIVINGSTONE Department of Geology, Royal Museum of Scotland, Chambers Street, Edinburgh EHI lJF

AND P. E. CHAMPNESS Department of Geology, The University of Manchester, Oxford Road, Manchester M13 9PL

Abstract Brianyoungite, which is chemically and structurally related to hydrozincite, occurs as white rosettes «100 [tm) with gypsum on rubbly limestone within the oxidised zone at Brownley Hill Mine, Nenthead, Cumbria. The mineral contains (wt.%) 71.47 ZnO, 9.90 C02, 6.62 S03 and 10.70 H20+. Basedon29oxygen atoms, the empirical formula is Znll_73[(C03hoo,(S04k10k IO(OH)15_88or ideally Zn3(C03,S04)(OHk Brianyoungite is either orthorhombic or monoclinic with p very close to 90°. Cellparameters determined by electron diffraction and refined from X-ray powder diffraction data are a= 15.724, b = 6.256 and c = 5.427 A. Density is > 3.93, < 4.09 glcm3 (meas.) and 4.11 glcm3 (calc.); Z=4. Thermogravimetric analysis, IR and XRD powder data (23 lines) are presented. KEYWORDS:brianyoungite, hydrozincite, Cumbria, new mineral.

Introduction mine, Nenthead, and from Vieille, Montagne, White rosettes «100[tm) of brianyoungite are Hollogne, Belgium, by XRD, XRF and IR and associatedwith gypsum on rubbly limestone, or has also been found associated with the zinc blackshaly coatings on limestone, within the analogue of schulenbergite (Livingstone et at., oxidisedzone at Brownley Hill Mine (NY 776 1992) from the Bastenberg mine, Ramsbeck, 447),Nenthead, Cumbria. The specimens were Germany. Both the mineral and the name were collectedunderground by Mr Brian Young in the approved by the LM.A. Commission on New disusedlead-zinc mine which is the type locality Minerals and Mineral Names before publication. foralstonite. Apart from oxidising pyrite with Holotype material is deposited within the Royal accompanyinggoethite and iron staining, the only Museum of Scotland Department of Geology, otherminerals noted are the rare zinc analogue of General Mineral Collection, under register ktenasite (Livingstone, 1991) and smithsonite. number 1992.17.1 and co-type material under Brianyoungite developed as individual rosettes 1992.17.2-8. onthesurface of specimens or within cavities, and as coalescences forming thin surface layers. Physical and optical properties Additionally,it may be encapsulated by gypsum. Thenew mineral developed from downward Extremely delicate brianyoungite rosettes (Fig. percolating waters transgressing rocks of the 1) consist of very thin (~1-2 [tm) blades which oxidisedzone through which the mine entrance taper to a sharp point in a similar manner to tunnelwas driven. hydrozincite. Individual blades are vitreous and The mineral is named after Brian Young transparent. Accurate determination of the (1947-), a field geologist and mineralogist with density proved difficult due to the small size of the British Geological Survey and author of individual blades or entrapped air in the rosettes. numerouspapers on the minerals of northern After approximately two hours the air bubbles England,who initially brought it to the attention escaped from single rosettes that had been Dfoneof the authors (A. L.). Brianyoungite has immersed in diluted Clerici solution contained in beenconfirmedon a specimen from Smallcleugh a cavity-mount microscope slide. A series of

Mineralogical Magazine, December 1993, Vol. 57, pp_ 665--670 @Copyright the Mineralogical Society 666 A. LIVINGSTONE AND P. E. CHAMPNESS

FIG. I.SEM photograph of brianyoungite rosettes on gypsum. Seale bar = 10 ~tm. diluted Clerici solutions of known densities were polish. Utilizing 1 mg aliquots ICP/OES and XRF prepared and rosettes added to each solution. In (EDS) analyses yielded 72.19 and 70.75 wI.% this way it was found that rosettes remained in ZnO respectively (average 71.47 wI. %). For the suspension in liquids of density >3.93 and <4.09 XRF analysis, 1 mg of brianyoungite was dis- g/cml. Because the grains always lay on the same solved in dilute HN03 acid and the solution face only two refractive indices could be meas- absorbed on a small disc of filter paper. The ured, i.e. 1.635 and 1.650 in NaD, (i:0.003). method was standardised by preparing pure ZnO Utilizing the calculated density and Gladstone- in the same way. The ICP/OES gave 6.62 wt.% Dale constants of Mandarino (1981) the calcu- SOl and a CHN analysis, on 1.115 mg, yielded lated refractive index is 1.747. The two measured 14.40 wt.% H20 total, plus 9.90 wt.% C02' refractive indices are therefore exand ~ respect- Thermogravimetric analysis showed that ively. All blades showed straight extinction. In absorbed moisture was 3.7 wI. %, which is a dilute acids, rapid dissolution with effervescence slightly high value, although Jambor (1964) occurred. The mineral does not fluoresce under suggested that the basic zinc carbonates may long- or short-wave ultraviolet light. Because of contain considerable absorbed water. From the the minute size of the crystals the hardness could following analysis-ZnO 71.47, C02 9.90, S03 not be determined. 6.62, and H20+ 10.70 wt.% (total 98.69 wt.%), on the basis of 29 oxygens, the empirical formula is Zn11dC03hoo(S04)IIO(OH)1588' The ideal Chemical, infrared and thermal studies formula -Zn dC03h(S04)(OH) 16 theoretically When analysed with a Camebax Cameca micro- requires ZnO 73.26, C02 9.91, S03 6.01, and probe, X-rayed polished rosettes revealed only H20 10.82 wt. %. This composition, if C03 and zinc and sulphur as major elements. Other S04 are combined, is similar to hydrozincite- elements detected include Cu, Mg, AI, Si, Ca and Zn5(C03h(OH)(" viz ZnO 74.12, C02 16.03, and Fe, which summed to approximately 0.3 wt. %; H20 9.85 wt. %. However, the possibility remains however, one spot analysis revealed 0.54 wt. % that sulphate is substituting for carbonate. The Mg. EPMA results varied widely from 61-63 ideal formula would then reduce to Zn3(C03, wt. % ZnO using a 10 ~tmline raster at 20 kY and 504)(OH)4' On this basis, from the empirical 10 nA to 69-82% ZnO on spot analyses at 20 kY formula, one quarter of the COl sites are filledby and 20 n A. These data reflect inherent difficulties 504, when undertaking this mode of analysis on highly The infrared spectrum (Fig. 2) reveals OH, hydrated, carbonated material that is difficult to COl and 504 absorptions. The spectrum bears a BRIANYOUNGITE. A NEW MINERAL 667 100. a ~~ 87.5 I ! J J J Q) 75.0 u i c: ro +J I r +J 62.5 I .M I I U)E i i r~ c ro I (. 50.0 . f-

~37.5 \ \ \ ! , I 25.0 \ ,AI / . ,I \ I \\) i i i II I ; ! 12.5 ~ U

0.0 ~--1 L--L.~ J . _.J J 1 1 L J.~J . ...1 1.._._ 4000 3200 2600 2000 1700 1400 1100 800 cm-1 200

FIG. 2. Infrared spectrum of brianyoungite. remarkable similarity to that of hydrozincite Because the crystals of brianyoungite were too although the OH absorptions of brianyoungite small for singlc crystal XRD, wc used electron are significantly shifted (~ 100 cm-I) towards diffraction in order to dctermine the unit cell higher wavenumbers. Comparison of the two parameters and to obtain information on the spectra reveals that brianyoungite is also a double space group. Rosettes were crushed in distilled carbonate structure with major C03 absorptions water and sedimented onto an electron micro- at ~ 1500 and 1380 cm -1. scope grid that was covered with a supporting film Thermogravimetric analysis (Fig. 3) revealed a of carbon. The sample was placed in a double-tilt series of overlapping regions of weight loss. The (:t60°, :t45°) holder and examined in a Philips firstloss (3.7 wt.%) up to 240°C is solely due to EM430 electron microscope operated at 300 kV. absorbed water. A major loss occurs between Thc grains showed no signs of degradation in the 320-450°C and is due to simultaneous evolution electron beam under these conditions. ofwater and some carbon dioxide. The next three In the TEM the crushed fragments appeared losses between 450 and 900°C involve both bladed and were of uniform thickness (Fig. 4a). carbon dioxide and sulphur dioxide. Total At zero tilt, the grains always gave a diffraction recorded loss is 36.8 wt. %. pattern identical to that shown in Fig. 4b. Thus the grains always lie on the same perfect cleavage face. The straight edges parallcl to the length of X-ray and electron diffraction studies the grains suggests that brianyoungite has a Several rosettes mounted on a spindle yielded second good cleavage. the X-ray powder data given in Table 1. Indi- The d-spacings, corresponding to the two vidual rosettes produce the same pattern which is shortest reciprocal lattice vectors in Fig. 4b, were characterised by very sharp lines. This sharpness calculated using an internal standard (i.e. by markedly contrasts with that of hydrozincite and evaporating pure gold onto the sample). Assum- other basic zinc carbonates (Jambor, 1964; 1966). ing that, by analogy with hydrozincite, the perfect Sections of the X-ray powder pattern show cleavage is (100), dUJlo)= 6.24 :t 0.04, dum) = similarities to those of hydrozincite, but there are 5.40 :t 0.04 A, (X*= 90°. With this indexing, the extra reflections that could not be indexed using crushed grains are elongated parallel to [010] and the cell parameters of hydrozincite. the second possible cleavage is (001). 668 A. LIVINGSTONE AND P. E. CHAMPNESS

110

100 .718 % 0.06745 mg)

14.41 % 90 (0.2614 mg)

4.654 % 80 (0.08443 mg)

4.564 % (0.08280 mg)

423 % (0.06210 g)

60 -1 o 200 400 600 800 1000 Temperature (Oe) FIG. 3. Brianyoungite thermogravimetrie analysis curve. heating rate lOoC/min.. in helium. The specimen was tilted away from the exact between the principal reciprocal axes. Thus we zone axis about the two principal reciprocal conclude that brianyoungite is either orthorhom- lattice directions in the [100] diffraction pattern. bic or monoclinic with a f3angle very close to 90'. On tilting about b* the OkOreflections with k odd, The (pseudo- )orthorhombic symmetry is also which arc weak in the [100] pattern (Fig. 4b), apparent in Fig. 4b in the distribution of intensity disappeared. This suggests that the reflections are of the diffraction spots which shows 2mm 'systematically absent' because there is either a symmetry. The lattice is primitive as there are no screw diad parallel to [010] or a b- or n-glide plane systematic absences in the hkl reflections. How- parallel to (001) and that the 'missing' reflections ever, the comparative weakness of the spots with only appear in the [100] pattern by double k odd in Fig. 4b, particularly at high angle, is an diffraction (e.g. 021 + 011 = 010). Tilting about indication of pseudo C-face centring. c* did not affect the intensities of the 001 Using the band c parameters derived by reflections, so there is neither a screw diad electron diffraction, it was possible to index the parallel to [001] nor a c- or n-glide plane parallel X-ray powder pattern as shown in Table 1. The to (010). refined cell parameters are: a = 15.724(3), b = No Kikuchi lines were observed in the diffraction patterns and the tilting experiments did not 6.256(5), c = 5.427(5) A, f3~90°, V = 534.01(3) A3, calculated density 4.11 glcm3. The cell reveal the Laue zones that would be expected of a perfect crystal. Rather, when the specimen was parameters for hydrozincite are: a = 13.554, b = tilted about either of the principal reciprocal 6.297, c = 5.404 A, f3 = 95.74°, V = 458.92 N axes in Fig. 4b, the other principal reciprocal axis (Effenberger and Pertlik, 1985). The indexing of merely appeared to increase in length. These the powder pattern confirms the lattice type of observations suggest that brianyoungite has some brianyoungite as primitive and the absence of a sort of disorder parallel to (100), ct. hydrozincite. 010 reflection, together with the lack of restric- When the grains were tilted about b* and c* no tions on hkO reflections, indicates the presence of deviation from 90° could be detected in the angle a screw diad parallel to [010] rather than a glide BRIANYOUNGITE, A NEW MINERAL 669 TABLE 1. X-RAY POWDER DATA FOR BRIANYOUNGITE powder patterns are very similar, they both show a bladed habit and have perfect (100) cleavage, and both are disordered parallel to (100) (which is I est. d meas.A d Calc.A hkl the result of both twinning and stacking disorder 100 15.44 15.72 100 in the case of hydrozincite (Ghose, 1964; Effen- 100 7.88 7.862 200 berger and Pertlik, 1985). This suggests that the 20 5.25 5.241 300 structures are closely related and that the space group of brianyoungite is probably either a 4.13 4.100) (011 4.018) (310 subgroup or a supergroup of C21m, the space group of hydrozincite. Of the possible space 5 3.944 3.931 400 groups listed above, P2j/m and P2j are both 10 3.128 3.128 020 subgroups, but P222t is not a supergroup of C21 10 2.976 3.068 120 10 2.907 2.906 220 m. However, definite identification of the space 10 2.802 2.809 510 group must await a full structure determination. Ghose (1964) found that, in hydrozin,cite, the 40 2.714 2.714) (002 2.710) (021 octahedral zinc atoms form chains parallel to [001]. The chains are joined together by sharing 10 2.661 2.671 121 an octahedral edge to form a sheet parallel to (100). Vacancies within the octahedral sheet are 20 2.577 2.565) (202 distributed on a rectangular 6.3 x 5.4 A (b-c) net. 2.562) (221 It seems highly probable that this same octahedral 2.4 78 2.489 012 sheet-structure is present in brianyoungite. The major difference between the cell para- 20 2.397 2.407) (321 meters of brianyoungite and hydrozincite is in the 2.373) (212 value of a, being 15.724 A for the former and 5 2.336 2.360 601 13.554 Afor the latter. The structure of hydrozin- 10 2.253 2.249 312 cite consists approximately of layers of oxygen/ 10 2.034 2.033 122 hydroxyl ions parallel to (100). There are six such layers, each one contributing four O/OH per unit 15 1.748 1.747) (900 1.744) (431 cell. As there are four more OH per unit cell in brianyoungite than in hydrozincite, this suggests 30 1.565b 1.566) (023 that there is an extra layer of O/OH in the cell of 1.564) (040 the former than in the latter and this allows the 1.563) (631 coordination of the two extra Zn atoms in the unit 10 1.547 1.543 812 cell of brianyoungite. The average spacing of the OIOH layers in hydrozincite is 2.26 A, which is 10 1.484 1.496) (141 roughly the difference between the a parametcrs 1.489) (603 1.476) (241 of hydrozincite and brianyoungite. 10 1.351 In all three of the possible space groups the 5 1.024 minimum number of equivalent positions in the unit cell is two. This suggests that the C03 and S04 groups occupy the same equivalent position, plane parallel to (001). There appear to be no i.e. that the S04 substitutes randomly for C03 as other systematic absences. happens III carrboydite, (Ni,Cu)6.9AI4.4~(S04' C03h7~(OHb.69 (Nickel and Clarke, 1976). Discussion The formula for brianyoungite can therefore be Brianyoungite is either orthorhombic or written: Zn3(C03,S04)(OH)4; Z = 4. monoclinic with ~close to 90°. If it is orthorhombic, the diffraction symbol is mmm f.2]-, which has only one possible space group, viz. P22j2, standard setting P2221. If, on the other hand, the mineral is monoclinic the diffraction symbol is Acknowledgements 21m P12j1 and there are two possible space Wc are indebted to Mr C. Chaplin for preparation of groups- P2jlm and P2j. The similarity between microprobe material and to the RMS Natural History the properties of brianyoungite and hydrozincite Department for the SEM usage. High-voltage TEM is striking; their band c cell-parameters are facilities were supported by NERC grant GR3/7197 to virtually identical, their IR spectra and X-ray P.E.C. 670 A. LIVINGSTONE AND P. E. CHAMP NESS

FIG. 4( a) Electron micrograph (300 k V) of two overlapping crushed grains of brianyoungite. (b) Electron diffraction pattern from the larger grain in (a) in the correct relative orientation.

References -Jackson, B.. and Davidson. P. J. (1992) The zinc analogue of schulenbergite, from Ramsbeck. Ger- Effenberger, H. Von and Pertlik. F. (1985) Verfeiner- many. Mineral. Mag., 56, 215-19. ung der Kristallstruktur des Hydrozinkits Mandarino, J. A. (1981) The Gladstone-Dale relation- ZnS(OH)6(CO,h- Osterrich. Akad. Wissenschft. ship: Part IV. The compatibility concept and its Math. Naturschft. Kl. Anzeiger 122, 9-11. application. Canad. Mineral.. 19. 441-50. Ghose. S. (1964) The crystal structure of hydrozincite, Nickel, E. H. and Clarke. R. M. (1976) Carrboyditc. a Zns(OH)r,(C03h Acta Crystallogr.. 17. 1051-7. hydrated sulfate of nickel and aluminium: a new Jambor. J. L. (1964) Studies of basic copper and zinc mineral from Western Australia. Amer. Mineral., 61, carbonates: I-synthetic zinc carbonates and their 366-72. relationship to hydrozineite. Can. Mineral.. 8, 92-108. -(1966) Natural and synthetic hydrozineites. Ibid.. 8.652-3. Livingstone, A. (1991) The zinc analogue of ktenasite from Smallcleugh and Brownley Hill mines, Nent- [Manuscript received /2 November /992: head. Cumbria. 1. Russell Soc.. 4,13-15. revised I2 March /993]