MINERALOGICAL MAGAZINE, MARCH 1986, VOL. 50, PP. 129 35 Chenite, Pb4Cu(SO4)2(OH)6, a new mineral, from Leadhills, Scotland W. H. PAAR Institut ffir Geowissenschaften (Mineralogie) der Universitfit Salzburg, Akademiestrasse 26, A-5020 Salzburg, Austria KURT MEREITER Institut ffir Mineralogie, Kristallographie und Strukturchemie der Technischen Universit/it Wien, Getreidemarkt 9, A-1060, Wien, Austria R. S. W. BRA1THWAITE Chemistry Department, University of Manchester Institute of Science and Technology, Manchester M601QD England PAUL KELLER Institut f/ir Mineralogie und Kristallchemie der Universit/it Stuttgart, Pfaffenwaldring 55, D-7000 Stuttgart 80, Federal Republic of Germany AND P. J. DUNN Department of Mineral Sciences, Smithsonian Institution, Washington, DC, USA 20560 ABSTRACT. Chenite, a new lead-copper secondary KEYWORDS: chenite, new mineral, Leadhills, Scot- mineral, has been found on specimens from the Leadhills land. area, Scotland. It is associated with caledonite, linarite, leadhillite, susannite, and other species, on oxidized galena with chalcopyrite. Electron microprobe analysis RECENTLY, two minerals have been reported yielded PbO 74.5, CuO 7.8, SO 3 13.3, H20 4.4 (by from the famous lead-zinc deposits of the Leadhills- difference), sum = 100 wt. ~o. The empirical formula Wanlockhead district, Scotland (Wilson, 1921; Gil- (based on 14 oxygens) is Pb3.gsCulA7S1.98014Hs.82; the landers, 1981; Paar, 1983)--scotlandite, PbSO 3 ideal formula is Pb4Cu(SO4)2(OH)6, which requires PbO (Paar et al., 1984), and macphersonite, a polymorph 75.2, CuO 6.7, SO 3 13.5, H20 4.6, sum = 100 wt. ~o. of leadhillite and susannite (Livingstone and Sarp, Infra-red spectroscopy showed the presence of only 1984). This paper reports on chenite, another new SO 2- and OH ions, with no H20. mineral from Leadhills, and it seems to be very Chenite is triclinic, P1 or P1, with a = 5.791(1), b = probable that this locality will provide further 7.940(1), c = 7.976(1) A, a = t12.02(1), fl = 97.73(1), y = 100.45(I) ~ V = 326.0 A 3, Z = 1. The strongest lines in the additions to the list of new minerals in the near X-ray powder diffraction pattern (d, I/Io, hkl) are: 5.55, 7, future. 100; 4.32, 6, lil; 3.60, 10 002; 3.41, 9, 120; 3.30, 5, 022; 3.00, In 1981 a small specimen was acquired by one of 5, 111; 2.80, 7, 122; 2.07, 6, 211/213/133; 1.778, 5, 312/2i3. us (W.H.P.) from D. M6hler (mineral dealer of Chenite forms minute, singly terminated, transparent Graz, Austria), displaying tiny, well-developed blue to translucent sky-blue crystals from 0.1 to over 1 mm crystals which subsequently turned out to be the long, elongated approximately 1-032]. Twenty different new mineral chenite. The specimen was labelled forms (pinacoids) have been identified on the four crystals 'Caledonit auf Bleiglanz; Susanna Mine, Leadhills, studied. A good cleavage on {100}, and traces of a second Schottland' and was accompanied by two old on {001}, can be observed. Optically, chenite is biaxial negative, 2 V(measured) = 67 + 1~ 2 V(calc.) = 68 ~ (Na). labels, one relating to the well-known mineral The refractive indices are ~ 1.871 + 0.005, fl 1.909 _+0.005, dealer J. B6hm of Vienna, and a second one 7 1.927+0.005 (Na). Dispersion is strong, r>> v. The indicating that the specimen was once part of the mineral is weakly pleochroic. H (Mohs) ~ 2 I. D = 5.98, world famous Karabaczek collection (Cassirer and and calculated D X= 6.044 g cm-3. Martin, 1979). (~ Copyright the Mineralogical Society 130 W. H. PAAR ET AL. This specimen measures approximately 3 • 3 x in size. A twinned crystal about 1.5 mm long is 289cm and consists predominantly of coarse- located at the deepest point of the cavity. The total grained galena with minor inclusions of chal- amount of chenite preserved on the specimen is copyrite. On one--the attractive--side, several between 8-12 mg. Pb-Cu secondary minerals have formed as a result The mineral has been named in honour of Dr of the decomposition of the primary ores. These T. T. Chen, mineralogist at CANMET, for his valu- include caledonite, the major phase, occurring as able contributions to the field of mineralogy. Both greenish-blue to bluish-green millimetre-sized the mineral and the name had been approved by the crystals rich in faces, and partly overgrown by IMA Commission on New Minerals and New linarite, which is present as poorly developed, Mineral Names prior to publication. intensively intergrown crystals less than 1 mm in Type material has been deposited in the collec- size, and crystal aggregates. On the reverse side of tions of the Smithsonian Institution, Washington, the specimen very limited amounts ofleadhillite are DC 20560, USA, the Royal Ontario Museum, visible as irregular plates displaying a pearly lustre Toronto, Canada, the Institut f/Jr Mineralogie und on the cleavage planes. Two unidentified phases Kristallchemie der Universit~it Stuttgart, Pfaffen- occur with the chenite; their identification has not waldring 55, D-7000 Stuttgart 80, Federal Republic been possible yet because of the trace amounts of Germany, the Institut fiir Mineralogie, Kristal- available, but a brief mention might be warranted: a lographie und Strukturchemie der Technischen white mineral forms a single cluster of needle-like Universit/it Wien, Getreidemarkt 9, A-1060 Wien, crystals about 0.2 mm long, perched on the chenite Austria, and the private collection of one of the twin, and a pale blue mineral forms radiating authors (W.H.P.). aggregates of hair-like crystals overgrowing the Subsequent to this investigation, a second speci- altered galena. Under the scanning electron micro- men of chenite from Susanna mine, containing scope the white mineral is seen to form elongated more and larger chenite crystals to over I mm in six-sided crystals capped with what appear to be length, has been purchased by one of us (W.H.P.). In hexagonal trapezohedrons. X-ray powder diffrac- addition to chenite this specimen contains susan- tion patterns of these phases did not match those of nite, green elongated prismatic leadhillite crystals, any published minerals. caledonite, hydrocerussite, linarite, lanarkite and The occurrence of chenite and the associated the above-mentioned white phase forming elon- unidentified species is restricted to a small cavity, gated six-sided crystals capped with hexagonal which is developed between weathered galena (with trapezohedrons, and is accompanied by two labels. micro-crystals of anglesite) and densely intergrown One from Mr M. Wright, FRGS, Great Russell St., crystals of caledonite forming the 'roof of the London, reads 'Suzannite, Suzannah mine, Lead- cavity. Within this cavity grew twelve chenite hills'; the other is from the collection of Docteur crystals, each less than 1 x 0.5 x 0.2 mm (0.1 mm 3) Latteux. FIG. la. Chenite crystals in parallel intergrowth, the largest approximately 1.2 mm long. The forms visiblecorrespond to those shown in fig. 2a, except that 253 is very poorly developed and not recognizable in the photograph. F~G. lb. Twinned chenite crystal about 1.5 mm long, the re-entrant angle being visible below the centre of the photograph. Associates include caledonite (background) and the white unknown mineral (clusters in foreground). The chenite twin cannot be removed without destroying it, nor can the specimen be used for mounting, to resolve the twin law of chenite. CHENITE, A NEW MINERAL 131 A further specimen of chenite has been discovered mentioned important zone [111], is usually the among material recently collected by R.S.W.B. and most prominent, followed by {010}, {001}, {101}, J. I. Wilson from an old slag dump at the site of the {111}, and {112}. In addition to the forms listed in ruins of Glengaber smelting mill at Meadowfoot, Table I a few very small ones were noted in the Wanlockhead, at the southern end of the Leadhills- vicinity of {221}; however, they could not be Wanlockhead orefield. This chenite, identified by indexed beyond doubt. infra-red spectroscopy, consisted of a cluster of tiny blue elongated prismatic crystals in a cavity in slag, associated with elyite, lanarkite and various other Table I. Crystallographic elements, angle table and optical oxidation products. This association of chenite orientation for chenite * with lanarkite, which is only thermodynamically Triclinic pinacoidal, (~) stable in environments low in carbonic acid (Abdul- Samad et al., 1982) suggests that the rarity of a:b:c = 0.7294 : I : 1.0045; ~112.02, ~ 97.73, ~100.45 ~ po:qo:ro = 1.2984 : 1.0122 : 1; % 65.81,/~77.17, ~ 75.38 ~ chenite, and presumably also of elyite, may be due P'o 1.4364, q'o 1.1198, x' o 0.1337, Y~o 0.4534 to the same limitation. In the presence of carbonate Reciprocal Cartesian matrix: i.1743 0 0.01701 the far more common caledonite is likely to be .0454 0.1404 0.0568J (in ~-1) formed in preference to chenite. 0 0.1254] Physical properties. Chenite forms minute single Forms (~ jo A B C (rarely twinned, fig. lb) and singly terminated, 0 0 1 16.67 25.33 77.17 65.81 transparent to translucent sky-blue crystals of 0 1 0 0.00 90.00 75.38 63.81 prismatic habit and roughly brick-like shape. They 1 0 0 75.38 90.00 75.38 77.17 are elongated approximately parallel to I032] I 1 0 43.16 90.00 32.23 43.16 67.49 -1 1 0 -61.41 90.00 136.80 61.41 84.93 (fig.