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Grguricite, CaCr2(CO3)2(OH)4.4H2O, a new alumohydrocalcite analogue
Mineralogical Magazine ( IF 2.8 ) Pub Date : 2020-09-01 , DOI: 10.1180/mgm.2020.66
M. S. Rumsey , M.D. Welch , J. Spratt , A.K. Kleppe

The occurrence and characterisation of a new member of the dundasite group are reported. Grguricite, ideally CaCr2(CO3)2(OH)4⋅4H2O, is the Cr analogue of alumohydrocalcite, CaAl2(CO3)2(OH)4⋅4H2O and occurs as lilac crusts of very fine-grained crystalline aggregates in the Pb–Ba–V mineralisation found at the Adeghoual Mine, Mibladen, Morocco (32°46′0″N, 4°37′59″W). The identification was based upon a close match with the powder X-ray diffraction data for alumohydrocalcite, the confirmation of anion components identified by Raman spectroscopy and the cation composition determined by electron-probe microanalysis. The empirical formula based upon 14 oxygen atoms per formula unit is Ca0.84Pb0.03Cr1.65Al0.39Mg0.02(CO3)2(OH)4⋅4H2O, with carbonate, hydroxyl and water contents set to those of the alumohydrocalcite stoichiometry. The fine-grained nature of the crystals (c. 0.5 μm × 0.1 μm × 5 μm) precluded a single-crystal X-ray study and both density and optical determinations. Grguricite is triclinic with space group P ${\bar 1}$ . Unit-cell parameters refined from the powder diffraction data are: a = 5.724(2), b = 6.5304(9), c = 14.646(4) Å, α = 81.682(1), β = 83.712(2), γ = 86.365(2)°, V = 537.8(2) Å3 and Z = 2. The five strongest peaks in the powder pattern are [dhkl, Å (I/Imax)(hkl)]: 6.222(100)(011), 3.227(87)(020), 6.454(63)(010), 2.883(58)(005, 023, 121) and 7.208(45)(002). The mineral is named after Australian geologist Ben Grguric.



中文翻译:

钙铝石CaCr 2(CO 32(OH)4 .4H 2 O,一种新型铝氢方解石类似物

有人报道了邓达斯特组新成员的出现和特征。Grguricite,理想CACR 2(CO 32(OH)4 ⋅4H 2 O,是alumohydrocalcite中的Cr类似物,CAAL 2(CO 32(OH)4 ⋅4H 2O发生在摩洛哥Mibladen的Adeghoual矿(32°46′0″ N,4°37′59″ W)中的Pb-Ba-V矿化中,是非常细粒度的晶体聚集体的丁香壳。鉴定是基于与氢氧化铝方解石的粉末X射线衍射数据紧密匹配,通过拉曼光谱法确定的阴离子成分的确认以及通过电子探针微分析法确定的阳离子组成的。基于每摩尔式单元14的氧原子的经验式为Ca 0.840.031.650.39的Mg 0.02(CO 32(OH)4 ⋅4H 2O,碳酸盐,羟基和水含量设定为铝氢方解石化学计量的那些。晶体的细粒度性质(约0.5μm×0.1μm×5μm)无法进行单晶X射线研究以及密度和光学测定。Grguricite是斜晶的,空间群为P $ {\ bar 1} $ 。从粉末衍射数据中提炼的晶胞参数为:a = 5.724(2),b = 6.5304(9),c = 14.646(4)Å,α= 81.682(1),β= 83.712(2),γ= 86.365(2)°,V = 537.8(2)埃3ž = 2。在粉末图案的五个最强峰为[ d HKL,A(/最大 )(hkl)]:6.222(100)(011),3.227(87)(020),6.454(63)(010),2.883(58)(005、023、121)和7.208(45)(002)。该矿物以澳大利亚地质学家Ben Grguric的名字命名。

更新日期:2020-09-01
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