Sentence:  Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled , That the Secretary of the Interior is hereby authorized and directed to establish and maintain a program of stabilization payments to small domestic producers of lead and zinc ores and <WSD>concentrates</WSD> in order to stabilize the mining of lead and zinc by small domestic producers on public , Indian , and other lands as provided in this Act . 
Meaning of the word marked with <WSD> tags:  the desired mineral that is left after impurities have been removed from mined ore