Palladium arsenide-antimonides from habira, Minas Gerais, Brazil

Abstract

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.

An unnamed platinum-group mineral from the Iluma Hill mine, Tanzania

“…Two quantitative microprobe analyses (CAMEBAX Microbeam) show that the mineral belongs to the Pd-As,Sb system and has the almost ideal formula Pds(As,Sb,Te)3 (Table 1). The data differ from those of arsenopalladinite (Clark et al, 1974;Cabri et al, 1977) and stillwaterite (Cabri et al, 1975) in its high antimony and tellurium content, suggesting a composition close to that of isomertieite (Clark et al, 1975). It was not possible to obtain X-ray data for the phase because of the small size of the grain.…”

Palladium oxides in ultramafic complexes near Lavatrafo, Western Andriamena, Madagascar

“…An apparent Pd-Hg oxide, which appeared to consist of N90% PdO and 10% HgO, was reported in heavy mineral concentrates from Itabira in Brazil by Clark et al (1974) and the mineral palladinite (PdO) was firmly identified for the first time in the Itabira concentrates by Jedwab et al (1993). The material is more extensively described in Jedwab (1995).…”

Palladium minerals from the Cauê iron mine, Itabira District, Minas Gerais, Brazil

“…We suggest that jacutinga is the most probable source of these palladium minerals because: arsenopalladinite and palladseite, two of the four minerals described by Clark et al (1974) were found in jacutinga; and the minerals described by these authors contain inclusions of palladium oxide and hematite which also occur in jacutinga.…”