Garavellite, FeSbBiS4, was found in a sample of the mineralogical collection of the Natural History Museum of the University of Florence. The sample is from the CuFe deposit of Caspari, Saverland, North Rhine-Westphalia, Germany. Garavellite occurs as very rare, elongated prismatic crystals up to 100µm in length, spatially associated with large berthierite crystals, bismuthinite, chalcopyrite, and siderite. It does not contain inclusions of or intergrowths with other minerals. Macroscopically garavellite is grey in colour and shows a grey-black streak. The Vickers hardness (VHN50) is 206kg/mm2. In plane-polarized incident light garavellite is grey in colour, with distinct bireflectance. Reflectance percentages for Rmin and Rmax are 33.8, 41.8 (471.1nm), 33.3, 40.9 (548.3nm), 32.7, 39.5 (586.6nm), and 32.4, 38.8 (652.3nm), respectively. Garavellite is orthorhombic, space group Pnam, with the following unit-cell parameters: a = 11.413(1) Å, b = 14.164(1) Å, c = 3.759(1) Å, V = 607.7(2) Å3, and Z = 4. Electron microprobe analyses give the chemical formula Fe0.94Cu0.01As0.01Sb1.02Bi0.99S4.03. The crystal structure has been solved and refined to R = 2.38%. It consists of FeS6 octahedra forming edge-sharing chains parallel to [001] with the Sb3+ and Bi3+ cations inserted between the chains. The crystal-chemical relationships with berthierite as well as the different lone-pair stereochemical activities of antimony and bismuth in the two structures are discussed.
Garavellite, FeSbBiS4, from the Caspari Mine, North- Rhine Westphalia, Germany: composition, physical properties and determination of the crystal structure.
2005
Abstract
Garavellite, FeSbBiS4, was found in a sample of the mineralogical collection of the Natural History Museum of the University of Florence. The sample is from the CuFe deposit of Caspari, Saverland, North Rhine-Westphalia, Germany. Garavellite occurs as very rare, elongated prismatic crystals up to 100µm in length, spatially associated with large berthierite crystals, bismuthinite, chalcopyrite, and siderite. It does not contain inclusions of or intergrowths with other minerals. Macroscopically garavellite is grey in colour and shows a grey-black streak. The Vickers hardness (VHN50) is 206kg/mm2. In plane-polarized incident light garavellite is grey in colour, with distinct bireflectance. Reflectance percentages for Rmin and Rmax are 33.8, 41.8 (471.1nm), 33.3, 40.9 (548.3nm), 32.7, 39.5 (586.6nm), and 32.4, 38.8 (652.3nm), respectively. Garavellite is orthorhombic, space group Pnam, with the following unit-cell parameters: a = 11.413(1) Å, b = 14.164(1) Å, c = 3.759(1) Å, V = 607.7(2) Å3, and Z = 4. Electron microprobe analyses give the chemical formula Fe0.94Cu0.01As0.01Sb1.02Bi0.99S4.03. The crystal structure has been solved and refined to R = 2.38%. It consists of FeS6 octahedra forming edge-sharing chains parallel to [001] with the Sb3+ and Bi3+ cations inserted between the chains. The crystal-chemical relationships with berthierite as well as the different lone-pair stereochemical activities of antimony and bismuth in the two structures are discussed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
