Surinamite analogs in the MgO-Ga2O3-GeO2 and MgO-Al2O3-GeO2 systems |
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Authors: | Jacques Barbier |
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Institution: | 1. Department of Chemistry, McMaster University, L8S 4M1, Hamilton, Ontario, Canada
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Abstract: | New germanate analogs of the mineral surinamite, Mg3Al4BeSi3O16, have been synthesized with composition Mg4A4Ge3O16 (A=Al, Ga) and have been characterized by powder X-ray diffraction and transmission electron microscopy. The Al surinamite phase crystallizes with a primitive unit-cell (P2/n, a=10.153(1), b=11.708(2), c=9.920(1) Å, β=110.18 (2)° and Z=4) similar to that of the silicate mineral. The Ga surinamite-like phase crystallizes with a larger unit-cell (C2/c, a=10.308(2), b=23.690(5), c=10.057(l) Å, β=110.23 (2)° and Z=8). High-resolution electron microscopy has shown the common formation of intergrowths between the surinamite and sapphirine structures, illustrating the polysomatic structural relationship between them. Observations of disordered microstructures in the Al surinamite suggest the occurrence of a P2/n?C2/c transformation. |
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