Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original Paper

Scharmová, Scharm

Rhabdophane group minerals in the uranium ore district of northern Bohemia (Czech Republic)

Journal of the Czech Geological Society, volume 39 (1994), issue 4, 267 - 280

Four mineral species of the rhabdophane group, namely: ningyoite, brockite, rhabdophane-(Ce), and rhabdophane-(Nd) are found in the sandstone type uranium ore district in the Bohemian Cretaceous Basin. Electron microanalyses indicate the existence of a continuous isomorphic series between ningyoite and brockite which is manifested by the unlimited mutual substitution of U and Th. However, there are pronounced differences in the habit and dimensions of the Th-bearing members on the one hand and the Th-free member (“pure” ningyoite) on the other. Rhabdophanes are characterized by a wide range of REE proportions. The occurrence of rhabdophane-(Nd), unusual La-free rhabdophane-(Ce) together with the earlier discovered phosphates, arsenates, and fluorocarbonates with Nd- and La-dominated composition indicate a distinctive fractionation of rare earth elements during exogenic processes.