X-RAY STUDIES OF SYNTHETIC COFFINITE, THORITE AND URANOTHORITES

Abstract

X-ray data are presented for synthetic coffinite, thorite, and several uranothorites. The cell constants obtained for coffinite are a = 6.981 plus or minus 0.004 kX, c = 6.250 plus or minus 0.005 kX; for thorite a = 7.128 plus or minus 0.004 kX, c = 6.314 plus or minus 0.003 kX. Intermediate constants determined for several uranothorites indicate a continuous solid solution between USiO/sub 4/ and ThSiO/sub 4/. Coffinite and thorite are isostructural with zircon; the space group is D//sub 4h//sup 19/ --I/sub 4/a md. The oxygen positions for coffinite are u = 0.180 plus or minus 0.010, v = 0.347 plus or minus 0.010 and for thorite u = 0.166 plus or minus 0.010 v = 0.347 plus or minus 0.010. No changes were observed either in line intensities or in cell constants when (OH) was removed from the hydrothermal preparations. (auth)