Description and crystal structure of fianelite, Mn2V(V,As)O7·2H2O, a new mineral from Fianel, Val Ferrera, Graubünden, Switzerland
Description and crystal structure of fianelite, Mn2V(V,As)O7·2H2O, a new mineral from Fianel, Val Ferrera, Graubünden, Switzerland
复制标题
瑞士格劳宾登州 Val Ferrera 的 Fianel 的新矿物 Mn2V(V,As)O7·2H2O 的描述和晶体结构
DOI：
10.2138/am-1996-9-1025
复制
发表时间：
1996
期刊：
影响因子：
--
通讯作者：
P. Berlepsch
中科院分区：
文献类型：
--
作者：
J. Brugger;P. Berlepsch
瑞士格劳本登瓦尔费雷拉的一个小矿山Fianel的铁锰矿石中产出铁锰石。它与石英、霓石和褐铁矿在横切石英+蔷薇辉石+钾镁矾+古褐帘石±霓石±绿帘石±透闪石±焦黄帘石细脉的薄开放裂缝中共生。只有少量非常微小的，片状的，（010）扁平的fianelite晶体已被收集。尖晶石晶体属P21/n空间群，a = 7.809（2），B = 14.554（4），c = 6.705（4），β = 93.27（3）°。X射线粉末图中最强的谱线为d 022，230 = 3.039，d120= 5.32，d231= 2.721和d163，362= 1.593 μ m。橙红色的矿物是透明的;它的光学符号是未知的，2 V很小。红透闪石具有从黄色到红色的强烈多色性。微探针分析显示，砷部分取代了钒，导致经验公式Mn1.98（V1.57As0.44Si0.01）O 7·2 H2O。fianelite的晶体结构，细化到R = 0.058，由锰的八面体链结合在一起的V对四面体。在两个V位置中，只有一个主机A。H存在于属于八面体的H2O基团中，并占据沿[001]沿着延伸穿过结构的通道。没有一种矿物的化学式与氟硅铝石的原子比例相同，但其结构特征却与氟硅铝石相似。
Abstract Fianelite occurs in iron and manganese ores at Fianel, a small mine in Val Ferrera, Graubunden, Switzerland. It is associated with quartz, aegirine, and limonite in thin open fractures crosscutting quartz + rhodonite + kutnohorite + palenzonaite ± aegirine ± parsettensite ± saneroite ± pyrobelonite veinlets. Only a small amount of very minute, tabular, (010)-flattened fianelite crystals have been collected. Fianelite, with ideal formula Mn2V(V,As)O7·2H2O, crystallizes in the P21/n space group with a = 7.809(2), b = 14.554(4), c = 6.705(4) Å and β = 93.27(3)°. The strongest lines in the X-ray powder pattern are d022,230 = 3.039, d120= 5.32, d231= 2.721, and d163,362= 1.593 Å. The orange-red mineral is transparent; its optical sign is unknown, and 2V is small. Fianelite shows a strong pleochroism from yellow to red. Microprobe analyses revealed a partial substitution of As for V, leading to the empirical formula Mn1.98(V1.57As0.44Si0.01)O7·2H2O. The crystal structure of fianelite, refined to R = 0.058, consists of Mn in octahedral chains bound together by pairs of V in tetrahedra. Among the two V positions, only one hosts As. H is present in H2O groups belonging to the octahedra and occupying channels extending through the structure along [001]. No mineral having a chemical formula with the same atomic proportions as fianelite shows similar structural features.