Nyerereite: a new volcanic carbonate mineral from Oldoinyo Lengai, Tanzania
Nyerereite: a new volcanic carbonate mineral from Oldoinyo Lengai, Tanzania
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Nyerereite：产自坦桑尼亚 Oldoinyo Lengai 的一种新火山碳酸盐矿物
DOI：
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发表时间：
1977
期刊：
影响因子：
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通讯作者：
E. Frankis
中科院分区：
文献类型：
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作者：
D. Mckie;E. Frankis
Nyerereite具有理想化的组成（Nao.s2Ko.18）2Ca（CO 3）2，其中SO 4-、PO 4-、F对CO 3的显著的少量取代，光学性质α = 1.5112，β = 1.5333，γ = 1.5345，2Fa = 29°，和密度2.541g cm-3。平均晶胞具有空间群Cmc 2 i，维度a = 5.044，B = 8.809，c = 12.743，并且包含四个分子式单元。非布拉格反射有h = η + mö，其中η和m是整数，δ = 0.383，表示结构调制。这种天然矿物是高温六方多晶型物的转化产物，高奈雷石，a = 5.05，c = 12.85 <$，空间群为P ^ m c。讨论了天然矿物（低镍铁矿）的平均结构，推测了高镍铁矿的结构。在Na 2Ca（CO 3）2-K2 Ca（CO 3）2体系中，除钠钙铝石外，所有相的高钠钙铝石结构都是亚里士多德型。讨论了该系统的矿物学命名。74 D U N C A N M C K I E和D E。J . F R A N K I S
Nyerereite has the idealized composition (Nao.s2Ko.i8)2Ca(C03)2 with significant minor substitution of S04", PO^ , F for CO3, optical properties α = 1.5112, β = 1.5333, γ = 1.5345, 2 F a = 29°, and density 2.541 g cm~3. The average unit cell has space group Cmc2i, dimensions a — 5.044, b = 8.809, c = 12.743 Ä and contains four formula units. Non-Bragg reflexions have h = η + mö where η and m are integers and δ = 0.383 and indicate a structural modulation. The natural mineral is an inversion product from a high-temperature hexagonal polymorph, high nyerereite with a = 5.05, c = 12.85 Ä and space group P ^ m c . The average structure of the natural mineral (low nyerereite) is discussed and the structure of high nyerereite is inferred. The high-nyerereite structure is the aristotype for all phases except buetschliite in the system Na2Ca(COs)2—K2Ca(CC>3)2. Mineralogical nomenclature in this system is discussed. 74 D U N C A N M C K I E a n d E . J . F R A N K I S