Nicheng Shi

Crystal structure of new micalike titanosilicate—bussenite, Na2Ba2Fe2+[TiSi2O7][CO3]O(OH)(H2O)F

AbstractThe crystal structure of mineral bussenite, Na2Ba2Fe[TiSi2O7][CO3]O(OH)(H2O)F, found in the Khibiny massif (the Kola Peninsula) has been determined. The parameters of the triclinic unit-cell are a = 5.399(3) Å, b = 7.016(9) Å, c = 16.254(14) Å, α = 102.44(8)°, β = 93.18(6)°, γ = 90.10(7)°, sp. gr.

Silicon-rutile — An ultra-high pressure (UHP) mineral from an ophiolite

P\bar 1

Linzhiite, FeSi2, a redefined and revalidated new mineral species from Luobusha, Tibet, China

, R = 0.054 for 1418 reflections with |F| > 2.5σ(F). The mineral studied belongs to the family of layered titanosilicates, in which, unlike the sulfate-and phosphate-containing representatives of this family, the interlayer spaces are filled with carbonate groups.

Structure Refinement of Monoclinic Astrophyllite

Abstract An unusual group of mantle minerals including about 70-80 species has been recovered from podiform chromitites of the Luobusa ophiolite, Qusong County, Tibet, China. All of the minerals were hand picked from heavy mineral separates of the chromitite. The minerals include diamond, coesite, moissanite, wüstite, intermetallic compounds, Os-Ir alloys with diamond inclusions, Fe-silicides, and a new mineral, qusongite. Qusongite is associated with chromian chlorite, calcite, (W,Ti)C and (Ti,W) C alloys, and chromite. It occurs as angular grains generally 4-8 μm in diameter, but some are as large as 0.2 × 0.3 × 0.25 mm. The grains are opaque and steel-gray with a metallic luster and grayish-yellow reflection. The empirical formula (based on 2 atoms) is W1.006Cr0.02C0.992, and the simplified formula is WC. Qusongite has a hexagonal structure and belongs to space group P6m2, with a = 2.902(1) Å, c = 2.831(1) Å, c:a = 0.9775, V = 20.05 (1) Å3, Z = 1.

Yarlongite:A New Metallic Carbide Mineral

Abstract Silicon(Si)-rutile separated from the Luobusa podiform chromitite in the Yarlung Zangbo ophiolite of southern Tibet is typically about 50 µm × 50 µm × 200 µm in size and consists mainly of SiO2 and TiO2. The average mineral formula is (Ti0.82Si0.18)O2. Powder X-ray diffraction data show that it is tetragonal in form, and the unit cell dimensions and other parameters are: a = 4. 591(2)A, c = 2.946 (2)A, v = 62.09(5)A3, c/a = 0.6415, with a molar volume about 5% smaller than rutile (JCPDS, 21–1276). The Si4+ ions in silicon rutile are six-coordinated, and are substituted for Ti4+ in the rutile structural sites. The Si-rutile, along with other associated ultra-high minerals discovered in the chromitite, such as octahedral silicate, silicon-magnesium spinel (Si4+ ions are six-coordinated), diamond, and intergrown of SiO2 and FeO phases, probably originated from the transition zone or the lower mantle, and were brought to shallow levels beneath an oceanic spreading ridge by an upwelling superplume.

The crystal structure of (Fe4Cr4Ni)9C4

The crystal structure of astrophyllite K2Na(Fe, Mn, Mg,□)7[Ti2(Si4O12)2|O3](OH, F)4 has been refined. The dimensions of the triclinic unit cell are: a = 0.5359(2) nm,b = 1.1614(4) nm, c = 1.1861(4) nm, α= 113.16(2)°, β= 103.04(2)°,γ= 94.56(2)°,V = 0.6495(5) nm3, Z= 1, space group P1, R=0.057 for 5308 reflections |Fo|>3σ|Fo|. According to structural and compositional differences the monoclinic astrophyllite K2NaNa(Fe, Mn)4Mg2Ti2[Si4O12]2(OH)4(OH, F)2 and astrophyllite should be considered as two different mineral species. Astrophyllite, monoclinic astrophyllite, bafertisite and lamprophyllite contain heteropolyhedral sheets which topologically are related with Si, O sheets of mica where one or several SiO4 tetrahedra are replaced by TiOn polyhedra. Therefore this heterophyllotitanosilicate series represents a kind of functional substitution in inorganic crystals.

Mineralogy and crystal structure determination of Mg-fillowite

“Ferdisilicite” (FeSi 2 ) was first described as a member of the Fe–Si alloy mineral series by Gevork’yan (1969), without CNMMN approval. It is redefined here as a new mineral, revalidated with the new name linzhiite with a CNMNC approval (IMA 2010-011). The type sample was found in a podiform chromitite from the Luobusha ophiolite in Tibet, People’s Republic of China. It occurs as irregular grains ranging from 0.04 to 0.5 mm in diameter and intergrowths with zangboite and native silicon. Linzhiite is steel grey in colour, opaque, with a metallic lustre and a greyish-black streak. The mineral is brittle and has a conchoidal fracture. Cleavage was not observed. The Mohs hardness is 6½, and the calculated density is 4.972 g/cm 3 . Reflectance values of the material in air ( R %) are: 26.3 at 470 nm, 30.3 at 546 nm, 32.9 at 589 nm, and 36.3 at 650 nm. The composition (mean of 12 EMP analyses) is Fe 49.09, Si 50.00, Al 0.64 and Mn 0.28 wt%, sum 100.01 wt%. The ideal formula is FeSi 2 . The crystal structure was refined from single-crystal X-ray diffraction data to R = 0.043. The mineral has a tetragonal P 4/ mmm structure, with a = 2.696 (1) A, b = 2.696 (1) A, c = 5.147 (6), V = 37.41 (14) A 3 , Z = 1. The five strongest X-ray powder diffraction lines [ d -spacing in A ( I / I 0 )] are: 5.136 (96), 2.374 (81), 1.896 (55), 1.849 (100), and 1.086 (36). Linzhiite formed in a strongly reducing environment and possibly occurs as xenocrysts derived from mantle sources.