Origin of birefringence in andradite from Arizona, Madagascar, and Iran

Antao, Sytle M.; Klincker, Allison M.

doi:10.1007/s00269-013-0594-4

Cited by 29 publications

(39 citation statements)

References 30 publications

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“…This result was very close to the result from chemical analysis. The chemical formula of the garnet is determined as Ca 3 (Fe 0.56 ,Al 0.44 ) 2 (SiO 4 ) 3 , which is calculated from the composition of An 56 Gr 44 [18]. This finding also shows a difference between the natural garnet used in our investigation and the andradite-grossular garnet and the grossular garnet from other research [19][20][21].…”

Section: Methodssupporting

confidence: 54%

Surface-Modified Garnet Particles for Reinforcing Epoxy Composites

Jiang

Liu

et al. 2018

Minerals

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The present study investigated the tribological performance of epoxy (EP) matrix composites enhanced with natural garnet. The garnet was surface-modified with sodium stearate for optimal performance. Composites comprising different contents and particle sizes of modified garnet (MG) were prepared with a mixture of EP and MG. The sodium stearate-bonded garnet and EP formed a stable structure. Tribological performance was measured by a ball-on-plate apparatus under permanent dry sliding conditions and a wear track was obtained by an optical profilometer. The wear mechanism was explored by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) images. Wear test results showed that the coefficient of friction for all EP/MG composites decreased compared with that for neat epoxy. The results also indicated that the addition of MG can evidently improve the tribological properties of EP matrix composites.

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Section: Methodssupporting

confidence: 54%

Surface-Modified Garnet Particles for Reinforcing Epoxy Composites

Jiang

Liu

et al. 2018

Minerals

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“…The three phase intergrowth in sample 3 was not observed in back-scattered electron (BSE) images, which is not unusual because all three phases have quite similar structural features and compositions. In the case of genthelvite and garnet-group minerals, multi-phase intergrowths were observed by splitting of diffraction peaks, but only sometimes were the different phases observed in BSE images (Antao and Hassan, 2010a;Antao, 2013;Antao and Klincker, 2013;Antao et al, 2015a,b;Antao and Cruickshank, 2016).…”

Section: Hrpxrd Traces and Satellite Reflectionsmentioning

confidence: 99%

Crystal Chemistry of Three Volcanic K-rich Nepheline Samples From Oldoinyo Lengai, Tanzania and Mount Nyiragongo, Eastern Congo, Africa

Antao

Nicholls

2018

Front. Earth Sci.

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Natural nepheline (Nph) samples are intermediate members of solid solutions that extend from the pure Na end-member Na[AlSiO 4 ] to the pure K end-member K[AlSiO 4 ] (=kalsilite, Kls). We examined two volcanic nepheline (ideally, K 2 Na 6 [Al 8 Si 8 O 32 ] or Nph 0.75 Kls 0.25) samples from Oldoinyo Lengai, Tanzania (samples 1 and 2) and a third sample 3 from Mount Nyiragongo, Eastern Congo. The crystal structure of these three samples was obtained using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinements in space group P6 3. Satellite reflections were not observed in these samples. The EPMA composition of sample 1 is {K 1.50 Na 0.19 Ca 0.07 0.23 } 2 (Na) 6 [Si 8.35 Al 7.48 Fe 0.18 ] 16.00 O 32. The A site contains 0.23 vacancies () with some Na and Ca atoms, whereas the B site is completely filled with only Na atoms. From the EPMA formula, K(sof) = 0.844 and Na(sof) = 1.0. The refinement unit-cell parameters are a = 10.00247(1), c = 8.38396(1) Å, V = 726.431(1) Å 3 ; K(sof) = 0.779(2) and Na(sof) = 0.988(2). The composition of sample 2 is {K 1.67 0.33 } 2 (Na 5.76 K 0.174 Ca 0.06) 6 [Si 8.44 Al 7.37 Fe 0.20 ] 16.01 O 32 , so K(sof) = 0.835 and Na(sof) = 1.030. Sample 2 has a = 10.01769(2), c = 8.39586(2) Å, V = 729.678(1) Å 3 , K(sof) = 0.812(2), and Na(sof) = 0.995(2). Sample 3 is a three-phase (3a, 3b, 3c) intergrowth with an average formula of {K 1.77 0.23 } 2 (Na 4.30 K 1.51 Ca 0.19) 6 [Si 8.13 Al 7.76 Fe 0.11 ] 16.00 O 32 , K(sof) = 0.887, and Na(sof) = 1.208. A large amount of K and Ca atoms occur in the B site. Based on the weight percentages and sofs of the three phases, the Rietveld refinement gives an average K(sof) = 0.859 and Na(sof) = 1.145. The average distances indicate a high degree of Al-Si disorder in samples 1, 2, and phase 3b. These African samples extend natural nepheline solid solutions to about Nph 0.55 Kls 0.45. The average distance increases linearly with Na(sof) and V across nepheline solid solutions because K atoms enter the Na site. K-rich nepheline seems to always contain vacancies in the A site.

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“…The hD-Oi distances (hD-Oi = {(Z-O) + (Y-O) + (X-O) + (X 0 -O)}/4) vary linearly with the a unit-cell parameter in cubic silicate garnets (Antao & Klincker, 2013). The linear dashed line for hD-Oi was fitted to data from Antao, Mohib et al (2015) and this study (Fig.…”

Section: +mentioning

confidence: 65%

“…Také uchi et al, 1982;Akizuki, 1984;Allen & Buseck, 1988;Angel et al, 1989;Kingma & Downs, 1989;Griffen et al, 1992;Nakatsuka, Yoshiasa, Yamanaka, Ohtaka, Katsura & Ito, 1999;Shtukenberg et al, 2001Shtukenberg et al, , 2005Wildner & Andrut, 2001;Frank-Kamenetskaya et al, 2007). Other suggested reasons for the birefringence in garnet were discussed (Antao & Klincker, 2013) and are not repeated here.…”

Section: Introductionmentioning

confidence: 91%

Two cubic phases in kimzeyite garnet from the type locality Magnet Cove, Arkansas

Antao

Cruickshank

2016

Acta Crystallogr Sect B

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The crystal structure of an optically anisotropic kimzeyite garnet from Magnet Cove, Arkansas, USA, where it was first discovered, was refined with the Rietveld method, cubic space group, Ia\overline 3 d, and monochromatic [λ = 0.41422 (2) Å] synchrotron high-resolution powder X-ray diffraction (HRPXRD) data. The Rietveld refinement reduced χ and overall R(F) values are 1.840 and 0.0647, respectively. The sample, with the general garnet formula XYZO, contains an intergrowth of two cubic phases that occur initially as oscillatory growth zoning, and patchy intergrowths arise later from fluid-enhanced dissolution and re-precipitation. The two compositions obtained with electron-probe microanalyses (EPMA) are Ca(ZrTiFeMn)[AlFeSi]O for phase 1a and Ca(ZrTiFe)[AlFeSi]O for phase 1b. The weight percentage, unit-cell parameter (Å), distances (Å), and site occupancy factors (s.o.f.s) for phase 1a are as follows: 42.6 (2)%, a = 12.46553 (3) Å, average 〈X-O〉 = 2.482, Y-O = 2.059 (2), Z-O = 1.761 (2) Å, Ca (X s.o.f.) = 0.960 (4), Zr (Y s.o.f.) = 0.809 (3), and Fe (Z s.o.f.) = 0.623 (2). The corresponding values for phase 1b are 57.4 (2)%, a = 12.47691 (2) Å, average 〈X-O〉 = 2.482, Y-O = 2.062 (1), Z-O = 1.762 (1) Å, Ca (X s.o.f.) = 0.957 (3), Zr (Y s.o.f.) = 0.828 (2) and Fe (Z s.o.f.) = 0.617 (2). The main structural differences between the two phases are in the unit-cell parameter, Δa = 0.01138 Å, Y(s.o.f.), and Y-O distance. Structural mismatch between the two cubic phases in a crystal gives rise to strain-induced optical anisotropy.

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Origin of birefringence in andradite from Arizona, Madagascar, and Iran

Cited by 29 publications

References 30 publications

Surface-Modified Garnet Particles for Reinforcing Epoxy Composites

Surface-Modified Garnet Particles for Reinforcing Epoxy Composites

Crystal Chemistry of Three Volcanic K-rich Nepheline Samples From Oldoinyo Lengai, Tanzania and Mount Nyiragongo, Eastern Congo, Africa

Two cubic phases in kimzeyite garnet from the type locality Magnet Cove, Arkansas

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