Carnotite was processed for at least two applications.
One was to obtain Radium, which is a trace element in the Uranium Oxide (that is Carnotite). The Curie's got a lot of their radium from the Carnotite ores of the Colorado-Utah area.
Carnotite was also used in glass making to make "vaseline glass" a common yellow glass, that was in vogue in the 1920-1930 era.
Vanadanite, the Vanadium ore, along with Carnotite, was also used in the pottery glazes in the very popular (and still popular) Fiesta dinner ware.