Crystal structure of morimotoite from Ice River, Canada

Antao, Sytle M.

doi:10.1017/s0885715614000414

Cited by 15 publications

(17 citation statements)

References 24 publications

(57 reference statements)

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“…The distances calculated from the cation radii (Shannon, 1976) are average <Ca-O> = 2.44, Ti-O = 2.02, Si-O = 1.69 Å, which are similar to those obtained from the Rietveld refinement (Table IV) Ca(X ) 1.14(1) 1.14(1) 0.57 (2) (Peterson et al, 1995). The Ice River sample was re-examined and similar cell and structural parameters to those obtained by Peterson et al (1995) were obtained by Antao (2014) ( Table IV).…”

Section: Rietveld Structure Refinementsmentioning

confidence: 53%

“…(Peterson et al, 1995;Armbruster et al, 1998;Chakhmouradian and McCammon, 2005), and that from Ice River as a solid-blue triangle (Antao, 2014). J. Michael Howard is thanked for providing a suite of schorlomite samples from Magnet Cove, Hot Spring Co., Arkansas.…”

Section: Acknowledgmentsmentioning

confidence: 99%

“…Ti-rich andradite is called "melanite" if it has <1 Ti apfu, and schorlomite if it has >1 Ti apfu (Deer et al, 1982;Locock et al, 1995). Chakhmouradian and McCammon (2005) examined the crystal structure of a schorlomite from the type locality in Magnet Cove, USA with a = 12.152(1) Å and contains 1.05 apfu Ti that are similar to the sample from Ice River, Canada with a = 12.157(3) Å and contains 1.06 apfu Ti (Peterson et al, 1995;Antao, 2014). It is difficult to tell the above species apart from each other as their compositional and structural data overlap.…”

Section: Introductionmentioning

confidence: 99%

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Schorlomite and morimotoite: what's in a name?

Antao

2014

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The crystal structure of an isotropic, single phase, Ti-rich schorlomite garnet, ideally Ca 3 Ti 4+ 2 (Fe 3+ 2 Si) O 12 , from Magnet Cove, Arkansas was refined with the Rietveld method, space group Ia3d, and monochromatic synchrotron high-resolution powder X-ray diffraction data. Electron-microprobe analysis gave an average composition {Ca 2.92 Na 0.04 Mn 2+ 0.03 Mg 0.01 } Σ3 [Ti 1.04 Fe 3+ 0.46 Mg 0.18 Fe 2+ 0.16 Zr 4+ 0.13 V 3+ 0.04 ] Σ2 (Si 2.21 Fe 3+ 0.71 Al 0.07 ) Σ3 O 12 , and corresponds to the general garnet formula of [8] X 3 [6] Y 2 [4] Z 3 [4] O 12 . Schorlomite is the dominant component, but the composition contains significant amounts (>15 mol.%) of andradite, Ca 3 (Fe 3+ 2 )Si 3 O 12 , morimotoite, Ca 3 (Ti 4+ Fe 2+ )Si 3 O 12, and morimotoite-(Mg), Ca 3 (Ti 4+ Mg)Si 3 O 12 . The crystal structure model was refined well using isotropic and anisotropic displacement parameters. Using isotropic displacement parameters, the χ 2 and R (F 2 ) Rietveld refinement values are 1.148 and 0.0742, respectively. The unit-cell parameter, a = 12.18599(1) (Å), is large for a natural schorlomite for which complete structural data are available. The bond distances are average = 2.4461, Ti-O = 2.0085(5), Si-O = 1.7022(5) Å, and site occupancy factors (sofs) for Ca(sof) = 0.963(1), Ti(sof) = 1.045(1), and Si(sof) = 1.150(2). Comparison of schorlomite data from the type locality in Magnet Cove with morimotoite from Ice River, Canada and the type locality in Japan show that they are quite similar and cast doubts as to morimotoite being different from schorlomite.

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Section: Rietveld Structure Refinementsmentioning

confidence: 53%

Section: Acknowledgmentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Schorlomite and morimotoite: what's in a name?

Antao

2014

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“…Additional details of the experimental setup are given elsewhere [29][30][31]. All of the above experimental techniques were used to characterize many minerals [32][33][34][35][36][37][38][39][40][41][42][43].…”

Section: Synchrotron High-resolution Powder X-ray Diffraction (Hrpxrd)mentioning

confidence: 99%

Structural Trends and Solid-Solutions Based on the Crystal Chemistry of Two Hausmannite (Mn3O4) Samples from the Kalahari Manganese Field

2019

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The crystal chemistry of two hausmannite samples from the Kalahari manganese field (KMF), South Africa, was studied using electron-probe microanalysis (EPMA), single-crystal X-ray diffraction (SCXRD) for sample-a, and high-resolution powder X-ray diffraction (HRPXRD) for sample-b, and a synthetic Mn 3 O 4 (97% purity) sample-c as a reference point. Hausmannite samples from the KMF were reported to be either magnetic or non-magnetic with a general formula AB 2 O 4 . The EPMA composition for sample-a is [Mn 2+ 0.88 Mg 2+ 0.11 Fe 2+ 0.01 ] Σ1.00 Mn 3+ 2.00 O 4 compared to Mn 2+ Mn 3+ 2 O 4 obtained by refinement. The single-crystal structure refinement in the tetragonal space groupI4 1 /amd gave R1 = 0.0215 for 669 independently observed reflections. The unit-cell parameters are a = b = 5.7556(6), c = 9.443(1) Å, and V = 312.80(7) Å 3 . The Jahn-Teller elongated Mn 3+ O 6 octahedron of the M site consists of M-O × 4 = 1.9272(5), M-O × 2 = 2.2843(7), and an average [6] = 2.0462(2) Å, whereas the Mn 2+ O 4 tetrahedron of the T site has T-O × 4 = 2.0367(8) Å. The site occupancy factors (sof ) are M(sof ) = 1.0 Mn (fixed, thereafter) and T(sof ) = 1.0008(2) Mn. The EPMA composition for sample-b is [Mn 0.99 Mg 0.01 ](Mn 1.52 Fe 0.48 )O 4 . The Rietveld refinement gave R (F 2 ) = 0.0368. The unit-cell parameters are a = b = 5.78144(1), c = 9.38346(3) Å, and V = 313.642(1) Å 3 . The octahedron has M-O × 4 = 1.9364(3), M-O × 2 = 2.2595(6), and average [6] = 2.0441(2) Å, whereas T-O × 4 = 2.0438(5) Å. The refinement gave T(sof ) = 0.820(9) Mn 2+ + 0.180(9) Fe 2+ and M(sof ) = 0.940(5) Mn 3+ + 0.060(5) Fe 3+ . Samples-a and -b are normal spinels with different amounts of substitutions at the M and T sites. The Jahn-Teller elongation, ∆(M-O), is smaller in sample-b because atom substitutions relieve strain compared to pure Mn 3 O 4 . Minerals 2019, 9, 343 2 of 16and in inverse spinels x = 1. A value of x = 2/3 corresponds to a random distribution of A and B atoms. Alternatively, an order parameter, Q, is used to express the degree of order [5]. The order parameter, Q, varies from Q = 1 for a completely ordered normal spinel to Q = 0 (where x = 2/3) for a random arrangement of cations to Q = −0.5 in inverse spinel. The relationship between Q and x is: Q = 1 -(3/2)x. Magnesioferrite, MgFe 2 O 4 , is partly inverse and partly normal, so it is one of the most interesting ferrite spinels [6][7][8].The structure of cubic spinels consists of T cations at 8a (1/8, 1/8, 1/8), M cations at 16d ( 1 /2 , 1 /2 , 1 /2 ), and O atoms on the body diagonals of a cube at 32e (u, u, u), where u is approximately 1 /4 in space group Fd3m. In a cubic spinel structure, there are only two structural variables (except displacement parameters): the a unit-cell parameter and the O atom positional parameter, u.Hausmannite, ideally Mn 3 O 4, is a normal spinel with a distorted tetragonal structure (Figure 1). End-member hausmannite structural formula is [4] [Mn 2+ ] [6] (Mn 2 3+ )O 4 . The T site may be occupied by divalent cations (e.g., Mn 2+ ...

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“…Recently, multiphase intergrowths of two or three cubic garnet phases also show split reflections (e.g. Antao, 2013b,a,c;Antao & Round, 2014;Schingaro et al, 2016;Antao, 2014a;Antao & Klincker, 2014;Antao, Mohib et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Crystal structure refinements of tetragonal (OH,F)-rich spessartine and henritermierite garnets

Antao

Cruickshank

2018

Acta Crystallogr B Struct Sci Cryst Eng Mater

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Cubic garnet (space group Ia\overline 3 d) has the general formula X 3 Y 2 Z 3O12, where X, Y and Z are cation sites. In the tetragonal garnet (space group I41/acd), the corresponding cation sites are X1 and X2, Y, and Z1 and Z2. In both space groups only the Y site is the same. The crystal chemistry of a tetragonal (OH,F)-rich spessartine sample from Tongbei, near Yunxiao, Fujian Province, China, with composition X (Mn2.82Fe^{2+}_{0.14}Ca0.04)Σ3 Y {Al1.95Fe^{3+}_{0.05}}Σ2 Z [(SiO4)2.61(O4H4)0.28(F4)0.11]Σ3 (Sps94Alm5Grs1) was studied with single-crystal X-ray diffraction and space group I41/acd. The deviation of the unit-cell parameters from cubic symmetry is small [a = 11.64463 (1), c = 11.65481 (2) Å, c/a = 1.0009]. Point analyses and back-scattered electron images, obtained by electron-probe microanalysis, indicate a homogeneous composition. The Z2 site is fully occupied, but the Z1 site contains vacancies. The occupied Z1 and Z2 sites with Si atoms are surrounded by four O atoms, as in anhydrous cubic garnets. Pairs of split sites are O1 with F11 and O2 with O22. When the Z1 site is vacant, a larger [(O2H2)F2] tetrahedron is formed by two OH and two F anions in the O22 and F11 sites, respectively. This [(O2H2)F2] tetrahedron is similar to the O4H4 tetrahedron in hydrogarnets. These results indicate ^{X}{{\rm Mn}^ {2+}_{3}}\,^{Y}{\rm Al}_{2}^{Z}[({\rm SiO}_{4})_{2}({\rm O}_{2}{\rm H}_{2})_{0.5}({\rm F}_{2})_{0.5}]_{\Sigma3} as a possible end member, which is yet unknown. The H atom that is bonded to the O22 site is not located because of the small number of OH groups. In contrast, tetragonal henritermierite, ideally ^{X}{\rm Ca}_{3}\,^{Y}{\rm Mn}^{3+}_{2}\,^{Z}[({\rm SiO}_{4})_{2}({\rm O}_{4}{\rm H}_{4})_1]_{\Sigma3}, has a vacant Z2 site that contains the O4H4 tetrahedron. The H atom is bonded to an O3 atom [O3—H3 = 0.73 (2) Å]. Because of O2—Mn3+—O2 Jahn–Teller elongation of the Mn3+O6 octahedron, a weak hydrogen bond is formed to the under-bonded O2 atom. This causes a large deviation from cubic symmetry (c/a = 0.9534).

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Crystal structure of morimotoite from Ice River, Canada

Cited by 15 publications

References 24 publications

Schorlomite and morimotoite: what's in a name?

Schorlomite and morimotoite: what's in a name?

Structural Trends and Solid-Solutions Based on the Crystal Chemistry of Two Hausmannite (Mn3O4) Samples from the Kalahari Manganese Field

Crystal structure refinements of tetragonal (OH,F)-rich spessartine and henritermierite garnets

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