A New Mineral, Scotlandite (Pbs03) from Leadhills, Scotland; the First Naturally Occurring Sulphite
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MINERALOGICAL MAGAZINE, JUNE 1984, VOL. 48, PP. 283-8 A new mineral, scotlandite (PbS03) from Leadhills, Scotland; the first naturally occurring sulphite W. H. PAAR Institut fur Geowissenschaften (Mineralogie) der Universitat Salzburg, Akademiestrasse 26, A-5020 Salzburg, Austria R. S. W. BRAITHWAITE Chemistry Department, University of Manchester Institute of Science and Technology, Manchester M60 lQD, England T. T. CHEN Mineral Sciences Laboratories, Canada Centre for Mineral and Energy Technology, 555 Booth Street, Ottawa, Ontario KIA OGl, Canada AND P. KELLER Institut fUr Mineralogie und Kristallchemie der Universitat Stuttgart, Pfaffenwaldring 55, 0-7000 Stuttgart 80, Federal Republic of Germany ABSTRACT. Electron microprobe analysis of the new angle p. H (Mohs) ".; 2. D = 6.37 and calculated D, = 6.40 mineral scotlandite yielded Pb 72.27, S 9.95, correspond- gcm-3. ing to PbO 77.85, S02 19.88, sum 97.73 wt. %. Secondary Scotlandite occurs in cavities in massive baryte and ion mass spectrometry showed the absence of Li, Be, B, C, anglesite, and is closely associated with lanarkite and N, and F, but the presence of very small amounts of Br. susannite; it represents the latest phase in the crystalliza- Infrared spectroscopy showed that the mineral is a tion sequence of the associated lead secondary minerals. sulphite with neither OH nor any other polyatomic The label locality of the specimen is the Susanna vein, anions. The empirical formula, calculated on the basis of Leadhills, Scotland. Pb+S = 2 is Pb1.06So.9402.94 or ideally PbS03. The mineral has the following vibrations of the sulphite ion in the infrared spectrum: v3 920, 865; v, 970 (?); V2 620, IN 1978 one of the authors (W.H.P.) acquired a 600; v4 488, 470 em-I. specimen labelled 'Lanarkite, Anglesite, Leadhillitej Scotlandite is monoclinic, with possible space groups Susannite; Susanna Vein, Leadhills, Lanarkshire, P2, or P2,/m. The unit cell dimensions are: a 4.542(2), b Scotland' from Dr D. H. Garske, at that time a 5.333(2), c 6.413(2) A, P 106.22(4)", Z = 2. The strongest resident of Elmhurst, Illinois, USA. It carries the lines in the powder diffraction pattern are: 3.99(10) (011), number S 0339 C. A short note on the label states 3.38(7) (110),3.25(8) (111), 3.07(4) (002), 2.66(7) (020, 012), 2.56(4) (112), 2.24(5) (121, 102), 2.01(5) (210, 022), 1.707(4) that the specimen was from the collection of (031), 1.538(4) (032, 004). Howard Belsky, of Brooklyn, New York, who Scotlandite occurs as chisel-shaped or bladed crystals obtained it from the late Richard Barstow in 1974. elongated along the c-axis, with a tendency to form The specimen is probably from an old collection, radiating clusters. The following forms have been deter- and is unlikely to have been collected in recent mined: {100}, {01O}, {Oll}, {021}, {031}, and {032}. The years. new mineral has a pronounced cleavage along {100}, Careful examination of the specimen revealed, in and a less good one along {01O}. The crystals are pale addition to the labelled species, the presence of tiny yellow to greyish-white and colourless, sometimes trans- crystals and crystal aggregates whose optical pro- parent. Their lustre is adamantine, pearly on cleavage perties and X-ray powder diffraction pattern did planes. The mineral is optically biaxial positive, 2Vrnm. 35° 24' not match those of any known mineral species. (Na).The refractive indices are: a ~ 2.035, P~ 2.040, and Subsequent electron microprobe analyses yielded y only lead and sulphur as detectable elements. The - 2.085 (Na). Dispersion is strong, v » r. The extinction (y: [100] is P//b, and a: [001] = 20" = 4°) in the obtuse chemical composition of the unknown phase was ~ Copyright the Mineralogical Society 284 W. H. PAAR ET AL. resolved by infrared spectroscopy, which indicated a sulphite mineral. This was confirmed by secon- dary ion mass spectrometry. Thus scotlandite represents the first naturally occurring sulphite. The mineral is named for Scotland. Both the mineral and the name have been approved by the Commission on New Minerals and Mineral Names, IMA, prior to publication. A preliminary examination of the Leadhills collections in both the British Museum (Natural History) and the Royal Scottish Museum has not yet brought to light another scotlandite specimen (J. P. Fuller and H. G. McPherson, resp., priv. comm., 1982). A thorough study of the Leadhills suite at the Museum of Natural History, Vienna, maintained by W.H.P. has not led to the discovery of more scotlandite either. Type material has been preserved at the Institut fur Geowissenschaften (Mineralogie), Universitiit Salzburg, Akademie- strasse 26, A-5020 Salzburg, Austria; the Institut fUr Mineralogie und Kristallchemie, Universitiit Stutt- gart, Pfaffenwaldring 55, D-7000 Stuttgart 80, FIG. I. Scotlandite crystals (approx. I mm), displaying the Federal Republic of Germany; the British Museum forms {021}, {03!}, {l00}, and {OlO}. In addition, the (Natural History), Cromwell Road, London, {100} cleavage is evident on the largest crystal, to the left. England; the Royal Scottish Museum, Edinburgh, Scotland; and the Royal Ontario Museum, Toronto, Canada. lanarkite. The susannite forms acute rhombohedral H. Sarp (priv. comm., 1983) has informed the crystals (2-3 mm) either isolated or as crystal authors of a second occurrence of scotlandite at clusters at various spots in the cavity. Argentolle mine, near Saint-Prix, Saone-et-Loire, Scotlandite is found in the vuggy anglesite as France. yellowish single crystals up to 1 mm in length (fig. It is notable that roeblingite was originally 1), which are sometimes arranged in fan-shaped formulated as a lead containing sulphite (Penfield aggregates. The colour results from minute inclu- and Foote, 1897), but was later shown by chemical sions of pyromorphite. A very thin coating of methods to be a sulphate free from sulphite (Blix, anglesite can usually be recognized on some of the 1931). Further revisions to the formula were pro- scotlandite and almost certainly protects the sul- posed by Foit (1966) and recently, from a number phite from further oxidation. A second variety of well-duplicated analyses, by Dunn et al. (1982) occurs in discontinuously distributed cavities to (Ca,Sr)dMn,Ca)2Pb4(S04)4SiI202s(OHb. In between the anglesite mass containing the first response to a suggestion by Dr M. H. Hey, two variety and the baryte matrix. This variety is specimens ofroeblingite from Franklin, New Jersey characterized by tiny, whitish to water-clear (one off BM 83806, and one from the W. H. Paar crystals and crystal clusters less than one millimetre collection) were studied by infrared spectroscopy, in size (fig.2a, b), which encrust large portions of the details of which are intended to be published interior of the cavities. separately. The spectra show strong sulphate V3 The morphology of the scotlandite is character- absorptions, but no strong absorptions distinctly ized by chisel-shaped crystals elongated along the attributable to sulphite. c-axis. The majority display the following forms: Descriptive mineralogy. The specimen (5 x 5 x prisms {021} and/or {031}; pinacoids {100} and 3 cm) consists of massive baryte with some 'limon- {01O}. Very rarely additional forms, such as the itic' coating on one side. A large cavity is developed prisms {Oll} and {032} can be determined (fig. 3). through the specimen and displays a variety oflead Equal development of all the reported prisms secondary minerals, including anglesite, lanarkite, around [lOOJ results in a somewhat rounded leadhillite, susannite, and the new mineral scot- appearance of the contours of {100}. Parallel landite. Lanarkite is present as elongated and intergrowths of scotlandite crystals after {IOO}and mostly cleaved prismatic crystals up to 1.5 cm long. star-like and compact radiating arrangements of Leadhillite crystals « 1mm) are thin tabular {001} such penetrating intergrowths can usually be ob- with a hexagonal outline, and are perched on the served (figs. 1, 2). SCOTLANDITE, A NEW MINERAL 285 FiG. 2. SEM photographs. (a, left) Parallel intergrowths of scotlandite crystals, the cluster measuring ~ 1 mm across. (b, right) A portion of the cluster shown in fig. 2a enlarged, displaying the typical spear-shaped habit of scotlandite crystals. Physical and optical properties. Scotlandite has a space group is either P21 or P2dm. The unit cell perfect cleavage along {100} and a good cleavage parameters obtained from the single crystal study along {OlD}. The lustre is adamantine, and pearly were used to index the X-ray powder pattern and on cleavage planes. Hardness (Mohs) is around 2. were then refined with the indexed powder data. The density, as determined with a Berman micro- The results are: a 4.542(2), b 5.333(2), c 6.413(2) A, balance on three fragments, weighing 5.4, 6.2, and f3 106.22(4t, Z = 2. If the present a and c axes are 6.8 mg respectively, is 6.37::!::0.02 g cm-3, in interchanged the unit cell of scotlandite is very excellent agreement with the density, Dx = 6.40 similar to that of molybdomenite, PbSe03 (Man- g cm- 3, calculated from its ideal formula. Com- darino, 1965). It appears that scotlandite is the pared with chemically related compounds, it is very sulphur analogue of the latter. The powder diffrac- closeto the value of anglesite (6.38 g cm- 3),but tion data of Table I were obtained using a 114.6 mm distinctly different from that of lanarkite (6.92 diameter Debye-Scherrer camera and Fe-KIXradia- g cm- 3);orthorhombic lead sulphite is of higher tion, filtered with Mn, without standards. Intensi- density (Dmeas= 6.54,calculated Dx= 6.56g cm- 3) ties were estimated visually.