• journal_title：Mineralogical Magazine
• Contributor：L. J. Cabri ; A. M. McDonald ; C. J. Stanley ; N. S. Rudashevsky ; G. Poirier ; B. R. Durham ; J. E. Mungall ; V. N. Rudashevsky
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2005-
• Format：text/html
• Language：en
• Identifier：10.1180/0026461056910236
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：69
• issue：1
• firstpage：89
• section：Articles

Naldrettite, Pd₂Sb, is a new intermetallic mineral discovered in the Mesamax Northwest deposit, Cape Smith fold belt, Ungava region, northern Québec. It is associated with monoclinic pyrrhotite, pentlandite, chalcopyrite, galena, sphalerite, cobaltite, clinochlore, magnetite, sudburyite (PdSb), electrum and altaite. Other rarer associated minerals include a second new mineral (ungavaite, Pd₄Sb₃), sperrylite (PtAs₂), michenerite (PdBiTe), petzite (Ag₃AuTe₄) and hessite (Ag₂Te). Naldrettite occurs as anhedral grains, which are commonly attached or moulded to sulphide minerals, and also associated with clinochlore. Grains of naldrettite vary in size (equivalent circle diameter) from ~10 to 239 μm, with an average of 74.4μm (n = 632). Cleavage was not observed and fracture is irregular. The mineral has a mean micro-indentation hardness of 393 kg/mm² It is distinctly anisotropic, non-pleochroic, has weak bireflectance, and does not exhibit discernible internal reflections. Some grains display evidence of strain-induced polysynthetic twinning. Naldrettite appears bright creamy white in association with pentlandite, pyrrhotite, clinochlore and chalcopyrite. Reflectance values in air (and in oil) for R₁and R₂ are: 49.0, 50.9 (35.9, 37.6) at 470 nm, 53.2, 55.1 (40.3, 42.1) at 546 nm, 55.4, 57.5 (42.5, 44.3) at 589 nm and 58.5, 60.1 (45.4, 47.2) at 650 nm. The average of 69 electron-microprobe analyses on 19 particles gives: Pd 63.49, Fe 0.11, Sb 35.75, As 0.31, and S 0.02, total 99.68 wt.%, corresponding to (Pd_1.995Fe_0.007)_2.002 (Sb_0.982As_0.014S_0.002)_0.998. The mineral is orthorhombic, space group Cmc2₁,a 3.3906(1), b 17.5551(5), c 6.957(2) A, V 414.097(3) ų, Z = 8. D_calc is 10.694(1) g/cm³. The six strongest lines in the X-ray powder-diffraction pattern [d in Å (I)(hkl)] are: 2.2454(100)(132), 2.0567(52)(043), 2.0009(40)(152), 1.2842(42)(115), 1.2122(50)(204) and 0.8584(56)(1.17.4).