Abstract
X-ray powder photographs and specific gravity determinations of specimens belonging to the uraninite-thorianite series and the pyrochlore-microlite series gave, for the former, a = 5.403-5.575 A (19 specimens), G = 6.43-9.55 (9), and for pyrochlore-microlite, a= 10.29610.441 A (5). Indexed powder data are given for uraninite and for ignited microlite. The powder pattern of orthorhombic euxenite (ignited at 1000° C), interpreted with the aid of established morphological descriptions, gave for this mineral, a=5.520, b = 14.57,c = 5.166 A, most probable space-group Pcmn, Z=4, G (meas.) = 5.23, ρ (calc for Y:Er = 2:1) = 5.58. An indexed powder pattern is given. Two specimens of “tanteuxenite” gave patterns of the uraninite type with a~5.10 A thus casting doubt on their identity with euxenite.
