Also called uraninite, a brown, black, or greenish mineral,
the most important source of uranium, radium,
and polonium. The composition of pitchblende
varies between UO2 and UO2.6; thorium,
lead, and helium
are also present. Principal deposits are in Zaire, Bohemia, at Great Bear
Lake, Canada, and in the Mountain States.
AND PLANETARY SCIENCE