Columbium ( niobium ) and tantalum were mined by Asyst Mines, Comptoirs Miniers de Burundi S . A ., Hamza, and Habonimana but the production of columbite-tantalite ore decreased considerably to 23, 356 kg in 2004 from 72, 441 kg in 2002 because low world market prices saw a slump in the demand for tantalum oxide in 2004.
