Chemours is selling its mining solutions business to the Czech cyanide maker Draslovka Holding for $520 million. The Chemours unit makes sodium cyanide, used to separate gold and silver from ore. The business had earnings before taxes of $52 million on sales of $203 million in 2020. Chemours said in March that it was considering the sale of the unit. The purchase, which the companies expect to close by the end of the year, marks Draslovka’s first major investment in the US.