Occurrence of Ishikawaite (Uranium-Rich Samarskite) in the Mineralized Abu Rushied Gneiss, Southeastern Desert, Egypt

Occurrence of Ishikawaite (Uranium-Rich Samarskite) in the Mineralized Abu Rushied Gneiss, Southeastern Desert, Egypt

Abstract
Ishikawaite, with an average assay of about 50% Nb2O5 and 26% UO2 has been identified for the
first time in Egypt in the mineralized Abu Rushied gneissose granite. The mineral is associated with
columbite, Hf-rich zircon, and dark Li-mica mineral (zinnwaldite). The mineralogy and geochemistry
of the studied ishikawaite were determined using microscopic investigation as well as quantitative
analysis by both field emission scanning electron microscope and electron microprobe analyses.
Analytical results indicate a structural formula of (U, Fe, Y, Ca) (Nb, Ta)O4 for the ishikawaite, with
U ranging from 0.12 to 0.61 per formula unit.