Scheuchzerite, Na(Mn,Mg)9[VSi9O28(OH)](OH)3, a new single-chain silicate
Scheuchzerite, Na(Mn,Mg)9[VSi9O28(OH)](OH)3, a new single-chain silicate
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Scheuchzerite，Na(Mn,Mg)9[VSi9O28(OH)](OH)3，一种新型单链硅酸盐
DOI：
10.2138/am.2006.1965
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发表时间：
2006
影响因子：
3.1
通讯作者：
T. Armbruster
中科院分区：
文献类型：
--
作者：
J. Brugger;S. Krivovichev;N. Meisser;S. Ansermet;T. Armbruster
摘要 Na(Mn,Mg)9[VSi9O28(OH)](OH)3 是一种新矿物，产自瑞士中部阿尔卑斯山 Val Ferrera 的 Fianel 变质同沉积喷出锰矿床。它是献给瑞士博物学家约翰·雅各布·舍赫泽（Johann Jakob Scheuchzer，1672.1733）的。白锰矿与矿脉中的硅锰矿和钛镁矿伴生，是由逆行第三纪高山变质作用期间矿石成分的再活化产生的。白辉石形成黄橙色透明针状晶体，长度可达 0.5 毫米，具有黄橙色条纹和玻璃光泽，莫氏硬度。硬度 ~2.5，dcalc 3.47（电子探针）至 3.52 g/cm3（结构细化）； dmeas 3.50(2) g/cm3，与纤维伸长平行的良好解理。白钨矿为正双轴，nmin = 1.74，nmax = 1.75； nmean（格拉德斯通-戴尔）1.74；弱多向色性，X = 棕黄色，Y = 浅黄色。经验化学式为Na0.97(Mn7.79Mg0.95Zn0.16Ni0.04Ca0.03Al0.01)Σ=8.98(V0.95As0.02Si9.08)Σ=10.05O32.05H4。白辉石为三斜晶系，P1̅，a = 9.831(5) Å，b = 10.107(5) Å，c = 13.855(7) Å，α = 86.222(10)°，β = 73.383(9)°，γ = 71.987(9)°； V = 1254.2(10) Å3; Z = 2。根据 1616 个 I > 4σF 的独特反射，用直接方法求解晶体结构，并精化至 R1 = 9.4%。晶体结构由四面体层组成，四面体层被包含边缘共享的 [Mn(O,OH)6] 八面体链以及 [NaO8] 多角体链的层分隔开。四面体层由沿[011]延伸的共角硅酸盐四面体的[Si9O25(OH)]环支链组成。这些环包含 6 个四面体，并由 3 个四面体分隔开，形成破碎的 4 环排列。氢原子可能由两个 O 原子共享（对称氢键），取代了缺失的硅原子。钒酸盐（VO4）3。四面体从 6-四面体环中分支出来，因此四面体链的整体分子式为 [VSi9O28(OH)]。在 Liebau (1985) 的表示法中，白沸石是单链硅酸盐（单聚硅酸盐）{olB1∞}[VSi9O28(OH)]。白沸石结构的拓扑结构让人想起角闪石族双链硅酸盐的拓扑结构，但白沸石含有一种新型的二氧化硅链。
Abstract Scheuchzerite, Na(Mn,Mg)9[VSi9O28(OH)](OH)3, is a new mineral from the metamorphosed synsedimentary exhalative Mn deposit of Fianel, Val Ferrera, Central Alps, Switzerland. It is dedicated to the Swiss naturalist Johann Jakob Scheuchzer (1672.1733). Scheuchzerite is associated with saneroite and tiragalloite in veins resulting from the remobilization of ore components during retrograde Tertiary Alpine metamorphism. Scheuchzerite forms yellow-orange, transparent acicular crystals up to 0.5 mm in length with yellow-orange streak and vitreous luster, Mohs. hardness ~2.5, dcalc 3.47 (electron microprobe) to 3.52 g/cm3 (structure refinement); dmeas 3.50(2) g/cm3, good cleavage parallel to fiber elongation. Scheuchzerite is biaxial positive, nmin = 1.74 and nmax = 1.75; nmean (Gladstone-Dale) 1.74; weakly pleochroic, X = brown yellow, Y = pale yellow. The empirical chemical formula is Na0.97(Mn7.79Mg0.95Zn0.16Ni0.04Ca0.03Al0.01)Σ=8.98 (V0.95As0.02Si9.08)Σ=10.05O32.05H4. Scheuchzerite is triclinic, P1̅, a = 9.831(5) Å, b = 10.107(5) Å, c = 13.855(7) Å, α = 86.222(10)°, β = 73.383(9)°, γ = 71.987(9)°; V = 1254.2(10) Å3; Z = 2. The crystal structure was solved with direct methods on the basis of 1616 unique reflections with I > 4σF and refined to R1 = 9.4%. The crystal structure consists of tetrahedral layers separated by layers containing chains of edge-sharing [Mn(O,OH)6] octahedra as well as [NaO8] polydedra. The tetrahedral layers consist of [Si9O25(OH)] loop-branched chains of corner-sharing silicate tetrahedra extending along [011]. The loops contain 6 tetrahedra and are separated by 3 tetrahedra in a broken 4-loop arrangement. A hydrogen atom is probably shared by two O atoms (symmetrical hydrogen bond), replacing the missing silicon atom. A vanadate (VO4)3. tetrahedron branches off the 6-tetrahedra loop, and hence the overall formula of the tetrahedral chains is [VSi9O28(OH)]. In the notation of Liebau (1985), scheuchzerite is a single chain silicate (monopolysilicate) {olB1∞}[VSi9O28(OH)]. The topology of the scheuchzerite structure is reminiscent of that of the double-chain silicates of the amphibole group, but scheuchzerite contains a new type of silica chain.