Molar volume and thermal expansion of glaucophane |
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| Authors: | David M Jenkins Juan-Carlos Corona |
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| Institution: | (1) Department of Geological Sciences and Environmental Studies, Binghamton University, Binghamton, NY 13902-6000, USA |
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| Abstract: | The molar volume of glaucophane Na2Mg3Al2Si8O22(OH)2] has been determined in this study by correcting synthetic glaucophane-rich amphiboles made in the system Na2O–MgO–Al2O3–SiO2–H2O for very small deviations from ideal glaucophane composition using recent volume data on key amphibole components. The derived unit-cell volume for end-member glaucophane is 862.7±1.6 Å3, which gives a molar volume of 259.8±0.5 cm3/mol and a calculated density of 3.016±0.006 g/cm3. This value has been corroborated through an essentially independent method by correcting the volumes of natural sodic amphiboles reported in the literature for non-glaucophane components, particularly including calcium-rich components, to yield a value of 861.2±1.9 Å3. The unit-cell volume derived from the synthetic amphiboles, which is considered here to be more reliable, is somewhat smaller than that reported previously in the literature. A thermal expansion (αV) at 298 K of 1.88±0.06×10?5/K was derived from unit-cell volumes measured in the range of 25–500°C for a synthetic glaucophane sample, which is noticeably smaller than previously reported. |
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| Keywords: | Glaucophane Sodic amphibole Volume Thermal expansion Nyb?ite |
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