Green andradite stones: gemmological and mineralogical characterisation

Adamo, Ilaria; Gatta, G. Diego; Rotiroti, Nicola; Diella, Valeria; Pavese, Alessandro

doi:10.1127/0935-1221/2011/0023-2079

Cited by 20 publications

(38 citation statements)

References 14 publications

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“…Samples Bal-1, 113-102 and And #27 are characterized by a main asymmetric OH À stretching band located at 3563 ± 1 cm À1 . This mode energy agrees perfectly with the IR results in Adamo et al (2009Adamo et al ( , 2011, but is different from that stated in Amthauer & Rossman (1998), where a value of 3555 cm À1 is presented (however, our reanalysis of these latter spectra gives a value of 3563 cm À1 ). Sample VM-11 gives spectra with one notable additional peak at 3605 cm À1 (see also Adamo et al, 2009Adamo et al, , 2011.…”

Section: Ftir Spectroscopysupporting

confidence: 83%

“…This mode energy agrees perfectly with the IR results in Adamo et al (2009Adamo et al ( , 2011, but is different from that stated in Amthauer & Rossman (1998), where a value of 3555 cm À1 is presented (however, our reanalysis of these latter spectra gives a value of 3563 cm À1 ). Sample VM-11 gives spectra with one notable additional peak at 3605 cm À1 (see also Adamo et al, 2009Adamo et al, , 2011. The spectrum of sample 4282 is radically different from the others, as it contains multiple low-intensity OH bands (cf., Amthauer & Rossman, 1998;Adamo et al, 2011).…”

Section: Ftir Spectroscopysupporting

confidence: 83%

“…Sample Bal-1, occurring as euhedral crystals with elongated {1 1 0} faces, from Balochistan, Pakistan, contains, as well, very small amounts of chrysotile and, in addition, tiny Cr-bearing magnetite crystals, as described by Adamo et al (2015). Sample 4282, whose locality is unknown to us (this andradite has a similar color and optical behavior and a very similar IR OH À -band spectrum to an andradite reported from Madagascar À Pezzotta et al, 2011, andAdamo et al, 2011), appears to be largely free of solid-inclusion phases. Of the different garnets that were studied, only the natural sample 113-102 and the two synthetics are optically isotropic.…”

Section: Sample Description and Optical Propertiesmentioning

confidence: 67%

“…Sample VM-11 gives spectra with one notable additional peak at 3605 cm À1 (see also Adamo et al, 2009Adamo et al, , 2011. The spectrum of sample 4282 is radically different from the others, as it contains multiple low-intensity OH bands (cf., Amthauer & Rossman, 1998;Adamo et al, 2011). The assignment for the asymmetric band at 3563 cm À1 is to a hydrogarnet substitution (Geiger & Rossman, 2018), whereas the other bands must represent OH À in an another structural site or cluster.…”

Section: Ftir Spectroscopymentioning

confidence: 99%

“…The crystal structures of both natural (Novak & Gibbs, 1971;Adamo et al, 2011) and synthetic andradite (Armbruster & Geiger, 1993) have been studied by Xray single-crystal diffraction and the two types are very similar structurally. The magnetic behavior of andradite from Val Malenco, Italy, was studied by low temperature 57 Fe-Mössbauer measurements (Murad, 1984), which show that the electron spins of the Fe 3þ cations order from the paramagnetic to antiferromagnetic state with a Néel transition temperature of 11.5 ± 0.1 K. The nature of this transition has also been investigated via ab initio calculations (Meyer et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Heat capacity and entropy behavior of andradite: a multi-sample and −methodological investigation

Geiger¹,

Dachs²,

Vielreicher³

et al. 2018

ejm

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Andradite, ideal end-member formula Ca 3 Fe 3þ 2 Si 3 O 12 , is one of the common rock-forming garnets found in the Earth's crust. There are several outstanding questions regarding andradite's thermodynamic and physical property behavior. Three issues are: i) Could there be differences in the thermodynamic properties, namely heat capacity, C p , between synthetic and natural andradite crystals, as observed in the Ca-garnet grossular, Ca 3 Al 2 Si 3 O 12 ? ii) What is the thermal nature of the low-temperature magnetic-phasetransition behavior of andradite? and iii) How quantitative are older published calorimetric (i.e., adiabatic and DSC) heat-capacity results? In this work, four natural nearly end-member single crystals and two synthetic polycrystalline andradite samples were carefully characterized by optical microscope examination, X-ray powder diffraction, microprobe analysis, and IR and UV/VIS single-crystal spectroscopy. The IR spectra of the different samples commonly show a main intense OH À stretching band located at 3563 cm À1 , but other OH À bands can sometimes be observed as well. Structural OH À concentrations, calculated from the IR spectra, vary from about 0.006 to 0.240 wt% H 2 O. The UV/VIS spectra indicate that there can be slight, but not fully understood, differences in the electronic state between synthetic and natural andradite crystals. The C p behavior was determined by relaxation calorimetry between 2 and 300 K and by differential scanning calorimetry (DSC) methods between 150/300 and 700/950 K, employing the same andradite samples that were used for the other characterization measurements. The low-temperature C p results show a magnetic phase transition with a Néel temperature of 11.3 ± 0.2 K, which could be slightly affected by the precise electronic state of Fe 2þ/3þ in the crystals. The published adiabatic calorimetry results on andradite do not provide a full and correct thermal description of this magnetic transition. The calorimetric C p measurements give a best estimate for the standard third-law entropy at 298.15 K for andradite of S o ≈ 324 ± 2 J/mol · K vs. the value of 316.4 ± 2.0 J/mol · K, as given in an early adiabatic investigation. Both natural and synthetic crystals give similar S o values within experimental uncertainty of about 1.0%, but one natural andradite, richer in OH, may have a very slightly higher value around S o ≈ 326 J/mol · K. Low-temperature DSC measurements made below 298 K agree excellently with those from relaxation calorimetry. The DSC measurements above 298 K show a similarity in C p behavior among natural and synthetic andradites. A C p polynomial for use above room temperature to approximately 1000 K was calculated from the data on synthetic andradite giving: C p (J/mol · K) = 599.09 (±14) À 2709.5 (±480) · T À0.5 À 1.3866 (±0.26) · 10 7 · T À2 þ 1.6052 (±0.42) · 10 9 · T À3 .

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Section: Ftir Spectroscopysupporting

confidence: 83%

Section: Ftir Spectroscopysupporting

confidence: 83%

Section: Sample Description and Optical Propertiesmentioning

confidence: 67%

Section: Ftir Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Heat capacity and entropy behavior of andradite: a multi-sample and −methodological investigation

Geiger¹,

Dachs²,

Vielreicher³

et al. 2018

ejm

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Electrode materials for calcium batteries: Future directions and perspectives

Masese,

Kanyolo

2024

EcoEnergy

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Despite the prevailing dominance of lithium‐ion batteries in consumer electronics and electric vehicle markets, the growing apprehension over lithium availability has ignited a quest for alternative high‐energy‐density electrochemical energy storage systems. Rechargeable batteries featuring calcium (Ca) metal as negative electrodes (anodes) present compelling prospects, promising notable advantages in energy density, cost‐effectiveness, and safety. However, unlocking the full potential of rechargeable Ca metal batteries particularly hinges upon the strategic identification or design of high‐energy‐density positive electrode (cathode) materials. This imperative task demands expeditious synthetic routes tailored for their meticulous design. In this Perspective, we mainly highlight the development in the cathode materials for calcium batteries and accentuate the unparalleled promise of solid‐state metathesis routes in designing a diverse array of high‐performance electrode materials.

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

Antao

Klincker

2013

Phys Chem Minerals

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Green andradite stones: gemmological and mineralogical characterisation

Cited by 20 publications

References 14 publications

Heat capacity and entropy behavior of andradite: a multi-sample and −methodological investigation

Heat capacity and entropy behavior of andradite: a multi-sample and −methodological investigation

Electrode materials for calcium batteries: Future directions and perspectives

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

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