35 research outputs found
A New Mineral Hanauerite, AgHgSI, and Common Crystal Chemical Features of Natural Mercury Sulphohalides
A new mineral, hanauerite, ideally AgHgSI, was found in the oxidation zone of Ag- and Hg-bearing ores at two old, abandoned mines in Rhineland-Palatinate, Germany. In a holotype specimen originating from the Schöne Aussicht Mine, Dernbach, Westerwald, it is associated with plumbogummiteâhinsdalite series of minerals and goethite. In cotype from the Friedrichssegen Mine, Bad Ems, it is associated with perroudite, goethite, and quartz. At both localities, hanauerite occurs as a prismatic crystal up to 0.15 mm long and up to 0.02 mm thick. The mineral is yellow, transparent, with an adamantine lustre. It is brittle, and cleavage was not observed. The calculated density values are 6.671 and 6.575 g cmâ3 for holotype and cotype, respectively. The empirical formulae calculated (from electron microprobe data) based on the sum of all atoms = 4 apfu are Ag0.95Hg1.00S1.01(I0.83Br0.19Cl0.03)ÎŁ1.05 for holotype and Ag0.97Hg0.97S1.05(I0.76Br0.25)ÎŁ1.01 for cotype. Hanauerite is orthorhombic, space group Pmma; the unit cell parameters (from single-crystal X-ray diffraction data; holotype/cotype) are: a = 9.932(2)/9.9256(8), b = 4.6219(19)/4.6209(2), c = 9.891(4)/9.9006(4) Ă
, V = 454.0(3)/454.19(5) Ă
3, and Z = 4. The crystal structure was studied on single crystals extracted from both holotype and cotype specimens; R1 = 0.0416 (holotype) and =0.0544 (cotype). In hanauerite, Hg2+ cations centre strongly distorted octahedra with two short HgâS bonds (Hg and S atoms build âcrankshaft-typeâ chains) and four strongly elongated HgâI bonds. The Hg-centred octahedra are connected via common edges and faces to form corrugated layers; Ag+ cations are located between these layers. Hanauerite is named in honour of the German mineral collector Dr. Alfred Hanauer (1912â1988). The common crystal chemical features of mercury sulphohalide minerals are discussed
Uma nova espécie de Cecidomyiidae (Diptera) associada com Sebastiania glandulosa (Euphorbiaceae) A new species of Cecidomyiidae (Diptera) associated with Sebastiania glandulosa (Euphorbiaceae)
Schizomyia spherica sp. nov., que induz galhas esfĂ©ricas em Sebastiania glandulosa, Ă© descrita e ilustrada com base em larvas, pupas, machos e fĂȘmeas de material coletado na restinga da Barra de MaricĂĄ (Rio de Janeiro, Brasil).<br>Schizomyia spherica sp. nov, that induces spherical galls on Sebastiania glandulosa, is described and illustrated based on larvae, pupae, males and females from the restinga of Barra de MaricĂĄ, Rio de Janeiro, Brazil