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 5 100 .718 % 0.06745 mg) 14.41 % 90 (0.2614 mg) 4.654 % 80 (0.08443 mg) 4.564 % (0.08280 mg) 70 423 % (0.06210 g) 60 -1 o 200 400 600 800 1000 Temperature (Oe) FIG.