Chemistry Discipline, Faculty of Science and Technology, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
Spectrochim Acta A Mol Biomol Spectrosc. 2012 Jun;91:301-6. doi: 10.1016/j.saa.2012.02.011. Epub 2012 Feb 10.
Arsenogorceixite BaAl(3)AsO(3)(OH)(AsO(4),PO(4))(OH,F)(6) belongs to the crandallite mineral subgroup of the alunite supergroup. Arsenogorceixite forms a continuous series of solid solutions with related minerals including gorceixite, goyazite, arsenogoyazite, plumbogummite and philipsbornite. Two minerals from (a) Germany and (b) from Ashburton Downs, Australia were analysed by Raman spectroscopy. The spectra show some commonality but the intensities of the peaks vary. Sharp intense Raman bands for the German sample, are observed at 972 and 814 cm(-1) attributed to the ν(1) PO(4)(3-) and AsO(4)(3-) symmetric stretching modes. Raman bands at 1014, 1057, 1148 and 1160 cm(-1) are attributed to the ν(1) PO(2) symmetric stretching mode and ν(3) PO(4)(3-) antisymmetric stretching vibrations. Raman bands at 764 and 776 cm(-1) and 758 and 756 cm(-1) are assigned to the ν(3) AsO(4)(3-) antisymmetric stretching vibrations. For the Australian mineral, the ν(1) PO(4)(3-) band is found at 973 cm(-1). The intensity of the arsenate bands observed at 814, 838 and 870 cm(-1) is greatly enhanced. Two low intensity Raman bands at 1307 and 1332 cm(-1) are assigned to hydroxyl deformation modes. The intense Raman band at 441 cm(-1) with a shoulder at 462 cm(-1) is assigned to the ν(2) PO(4)(3-) bending mode. Raman bands at 318 and 340 cm(-1) are attributed to the (AsO(4))(3-)ν(2) bending. The broad band centred at 3301 cm(-1) is assigned to water stretching vibrations and the sharper peak at 3473 cm(-1) is assigned to the OH stretching vibrations. The observation of strong water stretching vibrations brings into question the actual formula of arsenogorceixite. It is proposed the formula is better written as BaAl(3)AsO(3)(OH)(AsO(4),PO(4))(OH,F)(6)·xH(2)O. The observation of both phosphate and arsenate bands provides a clear example of solid solution formation.
砷戈氏砷铝矿 BaAl(3)AsO(3)(OH)(AsO(4),PO(4))(OH,F)(6) 属于明矾石矿物亚族的明矾石超族。砷戈氏砷铝矿与相关矿物（包括戈氏砷铝矿、戈尔西矿、砷戈西矿、铅矾和菲利普斯伯尔尼矿）形成连续的固溶体系列。对来自德国和澳大利亚阿什伯顿唐斯的两种矿物进行了拉曼光谱分析。光谱显示出一些共性，但峰的强度有所不同。德国样本的尖锐强拉曼带在 972 和 814 cm(-1)处归因于 ν(1)PO(4)(3-)和 AsO(4)(3-)对称伸缩模式。在 1014、1057、1148 和 1160 cm(-1)处的拉曼带归因于 ν(1)PO(2)对称伸缩模式和 ν(3)PO(4)(3-)反对称伸缩振动。在 764 和 776 cm(-1)和 758 和 756 cm(-1)处的拉曼带被分配到 ν(3)AsO(4)(3-)反对称伸缩振动。对于澳大利亚矿物，ν(1)PO(4)(3-)带位于 973 cm(-1)处。观察到的砷酸盐带在 814、838 和 870 cm(-1)处的强度大大增强。在 1307 和 1332 cm(-1)处的两个低强度拉曼带被分配到羟基变形模式。在 441 cm(-1)处的强拉曼带带有 462 cm(-1)处的肩峰被分配到 ν(2)PO(4)(3-)弯曲模式。在 318 和 340 cm(-1)处的拉曼带归因于 (AsO(4))(3-)ν(2)弯曲。位于 3301 cm(-1)处的宽带归因于水伸缩振动，位于 3473 cm(-1)处的较尖锐峰归因于 OH 伸缩振动。强水伸缩振动的观察对砷戈氏砷铝矿的实际公式提出了质疑。建议更好地将公式写成 BaAl(3)AsO(3)(OH)(AsO(4),PO(4))(OH,F)(6)·xH(2)O。磷酸和砷酸盐带的观察提供了固溶体形成的清晰实例。
