Abstract
Fully ordered columbite-(Mn), tantalite-(Mn), hafnon, and zircon were successfully synthesized using an acid solution of 6N:1N (N = normal) HF:H 2 SO 4 and stoichiometric oxide mixtures. The mixtures and solutions were sealed and placed in rapid-quench cold-seal pressure vessels (CSPV) at 800–850 °C and 200 MPa. Mineral structures and compositions have been confirmed by scanning electron microscope (SEM), micro X-ray diffraction (μXRD), and electron probe microanalysis (EPMA). The unit cell parameters of the minerals determined by μXRD: Orthorhombic ( Pbcn ) columbite-(Mn) a 14.434(2), b 5.768(1), c 5.084(1) A; orthorhombic ( Pbcn ) tantalite-(Mn) a 14.457(3), b 5.773(1), c 5.096(1) A; tetragonal hafnon ( I 4 1 /amd ) a 6.582(2), c 5.9702(1) A; and tetragonal zircon ( I 4 1 /amd ) a 6.607(4), c 5.9898(2) A. The chemical formulae as determined by EPMA are very close to stoichiometric: Mn 0.96 Nb 2.02 O 6 , Mn 0.99 Ta 2.01 O 6 , Hf 0.99 Si 1.01 O 4 , and Zr 1.00 Si 1.00 O 4 , respectively.
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