Molar volumes of mixing of almandine-pyrope and almandine-spessartine garnets and the crystal chemistry and thermodynamic-mixing properties of the aluminosilicate garnets

Magnetic structure of almandine

“…This cluster is constructed on the base of the (Table 2), reflecting their identical atomic environment and equal lattice sites. Furthermore, the value of the quadrupole splitting of -3.53 mm s -1 is in quantitative agreement with the Mössbauer measurements (Murad and Wagner 1987;Geiger et al 1992;Woodland and Ross 1994;Geiger and Feenstra 1997). Subsequent increase in the cluster size from 79 to 118 atoms leads to oscillatory changes of the values of Heisenberg coupling constants and quadrupole splitting.…”

“…-cation are compared with the measured absorption and Mössbauer spectra ( Table 1). The results are in quantitative agreement for the quadrupole splittings obtained by Mössbauer spectroscopy (Murad and Wagner 1987;Geiger et al 1992;Woodland and Ross 1994;Geiger and Feenstra 1997) within the expected error margins of 20% for this type of calculations, whereas the d-d energies are somewhat smaller than the respective experimental values (Clark 1957;Geiger and Rossman 1994;White and Moore 1972;Manning 1967).…”

“…Al 2 Si 3 O 12 -Mg 3 Al 2 Si 3 O 12 join have already been studied experimentally by several workers using absorption spectroscopy (Clark 1957;Geiger and Rossman 1994;Manning 1967;White and Moore 1972), Mössbauer spectroscopy and measurements of the magnetic properties (Murad and Wagner 1987;de Oliveira et al 1987de Oliveira et al , 1989Geiger et al 1992;Anovitz et al 1993;Woodland and Ross 1994;Geiger and Feenstra 1997). The optical and near-to-mid-IR spectra of almandine show a threeband system in the near infrared at about 4,350 cm -1 , 5,850 cm -1 and 7,600 cm -1 (Clark 1957;Geiger and Rossman 1994;Manning 1967; White and Moore 1972) that has been attributed to spin-allowed d-d transitions of Fe 2?…”

Influence of Chemical Composition and Water on the Bulk Modulus of Pyrope

“…This study was a systematic investigation on the pyrope-almandine binary system. A relation between the bulk modulus and the almandine mole fraction (n) was derived to be K 0 = 170 + 15 n. We concluded that this system is close to an ideal mixing model, which agrees with Geiger et al, (1997), who studied volume mixing and thermodynamic parameters of garnet in the pyrope-almandine join.…”

“…This may be attributed to unidentified phases in natural samples. Geiger et al, (1997) reported the volume mixing along Py-Alm join is ideal. Therefore a simple ideal mixing model ( = + ; n 1 , n 2 : mole fraction of pyrope and almandine) is used to fit our bulk modulus data.…”