Synopsis Mattheddleite, a new lead member of the apatite group with sulphur and silicon totally replacing phosphorus, occurs as tiny crystals (<0.1 mm) forming drusy cavities in specimens from Leadhills. Optically, the mineral is colourless in transmitted light and is uniaxial with ω2.017 and ε1.999. X-ray powder diffraction data are similar to the synthetic compound lead hydroxyapatite and may be indexed on a hexagonal cell with a 9.963 and c 7.464 Å (the cell volume is 642 Å 3 ). The calculated density is 6.96 g/cm 3 . The strongest lines in the powder pattern are [ d , ( I ) ( hkl )]: 2.988 (100) (112, 211), 4.32 (40) (200), 4.13 (40) (111), 2.877 (40) (300), 3.26 (30) (210). Single crystal Weissenberg photographs are close to those of pyromorphite, space group P6 3 /m. Chemically, mattheddleite does not contain S and Si in the expected 1:1 ratio, and the ideal formula may be expressed as Pb 20 (SiO 4 ) 7 (SO 4 ) 4 Cl 4 . The infrared spectrum is very similar to that of hydroxyellestadite. Associated minerals are lanarkite, cerussite, hydrocerussite, caledonite, leadhillite, susannite, and macphersonite. The mineral is named after Matthew Forster Heddle (1828–1897), a famous Scottish mineralogist.

SUMMARY. The arsenopalladinite concentrates from Itabira, Minas Gerais, Brazil, have been found to contain three arsenide-antimonides of palladium, namely arsenopalladinite, atheneite, and isomertieite. The second and third of these are new minerals.Arsenopalladinite, redefined, is Pds(As,Sb)2 and triclinic with a 7'399, b I4'o63, c 7.352/~, c~ 920 03', fi I I8 ~ 57', ~' 95 ~ 54'. Z = 6. Dmeas = IO'4, Dcalc = I0"46. In reflected light arsenopalladinite is white with a yellowish creamy hue. The mineral shows complex polysynthetic twinning and is strongly anisotropic. Reflectance measurements at 47o, 546, 589, and 65o nm respectively gave: in air, [46][47][48][49][50][51][52][52][53][54][55][56][57] in oil,[32][33][34][35][37][38][39][40][41][42][43] av. In reflected light isomertieite is a pale yellow colour. One grain was isotropic, three others displayed weak anisotropy. Untwinned. Reflectance measurements at 47o, 546, 589, and 65o nm gave respectively: in air, [44][45][46][52][53][55][56][57][56][57][58][59][60][61][62] in oil,[42][43][44][45] av. 592. Quantitative colour values are also given, and the chemical and optical properties are compared with the related mineral, stibiopalladinite.EARLY in ~934 Bernard Hall Sanders of Redruth, Cornwall, left for examination at the British Museum (Natural History) five mineral specimens he had acquired from Brazil. One of these, consisting of 4 g of residual concentrates from the gold washing at Itabira, Minas Gerais, aroused immediate interest since the preliminary analysis showed the major element to be palladium although an X-ray diffraction photograph did not correspond with any known palladium mineral. Sanders had blowpipe tests carried out on several portions of the concentrates and obtained an arsenic residue which led him to suggest that the mineral was a palladium arsenide. This was confirmed by chemical analyses made subsequently by M. H. Hey and, although the analyses showed a variable concentration of Pd, the formula PdsAs was suggested for the mineral together with the name arsenopalladinite, thus linking it compositionally 9 Crown copyright reserved.

IN the course of a continuing review of rare minerals that have been reported from the British Isles, we have examined Cornish specimens that purported to be the bismuth silicate, eulytine (Collins, 1881). Two localities are involved: the Restormel (also Royal) iron mine, near Lostwithiel, noted for its remarkable goethite crystals; and Wheal Coates, St Agnes, best known for its pseudomorphs of cassiterite after orthoclase. Collins' specimens, one from each locality (nos. 1588 and 1589, respectively), are in the mineral collection of the Royal Institution of Cornwall, Truro; and another Restormel specimen (BM 32875, Talling no. 614) is in that of the British Museum (Natural History). Specimens from both localities are rather unprepossessing, showing some 'bismuth ochre'. Only on the Restormel material are there a few small, shining crystals, which have proved to be waylandite, a member of the crandallite group; but we have found no eulytine (Macpherson, 1983, p. 249). The dealer Richard Talling, who supplied the BM specimen in 1861, invoiced the crystals as being 'bismuth blende' (= eulytine) and thus seems to be responsible for the original identification, presumably on the basis of appearance and association. A second Talling specimen was acquired as bismutite with the Russell collection (BM 1964R, 7185), and the exact fit of its broken surface shows that if is the 'other half' of BM 32875. It bears the printed number 765, with solid lines above and below, in contrast with the handwritten no. 614; and it is instructive to note that Talling used written numbers for the best specimens he sold, with a different sequence of printed ones for those that he considered less good. The Wheal Coates specimen (RIC no. 1589) has neither waylandite nor eulytine on it, and the earthy mineral gives a clear X-ray powder pattern of bismutite, the basic carbonate of bismuth. Similar material was first examined by the Revd W. Gregor, in about 1809, who supplied the specimen described as an earthy steatite-like mineral and figured in Sowerby's British Mineralogy (Vol. IV, 1811). The status of this material as a carbonate was doubted by Beudant (1832), and later by Greg and Lettsom (1858), but was accepted by Brooke and Miller (1852) who named it agnesite for the locality. It would seem that Gregor (misnamed 'Macgregor'

ABSTRACT. Sweetite, naturally occurring Zn(OH)2 with tetragonal symmetry, has been found at Milltown, near Ashover, Derbyshire. It occurs as colourless or whitish bipyramids up to 1 mm in size scattered over the surface of colourless fluorite cubes. The cell dimensions are a 8,222 and c 14.34A with Z = 20. The strongest lines of the X-ray powder pattern are (d, I, hkl) S WE E X I X E was first found in February 1982 by M r S. A. Rust at a disused limestone quarry 200-300 m north-west of the village of Milltown near Ashover in Derbyshire. It occurred in an oxidized area of a vein exposure on the north-western face of the quarry, the unaltered material consisting of fluorite veined with calcite. The sweetite crystals were found in the first 30 cm of the oxidized area above the quarry floor, between two narrow veins of fluorite, sprinkled over the face of colourless fluorite cubes in cavities several centimetres in diameter. Other cavities carried altered galena with anglesite and cerussite while hydrocerussite and litharge have also been found in the oxidized area. Joints in the fluorite veins were covered in a white encrusting mineral identified as attapulgite.

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