The combined acid, scrap and treatment charges for the cement copper
resulted in an operating cost in excess of $300/t of metal; higher than a normal sulphide operation would be.
Then, in the 1980s, Leonor was purchased by Minera Cobrenorte Ltda and underground mine development began, together with the construction of a small plant producing cement copper
. In 1991, Equatorial Mining executed an option to purchase the L eonor property, establishing Compania Contractual Minera Leonor (CCML).
The pregnant solution is pumped from there to the cementation tanks where scrap iron is added to obtain cement copper.
Final cement copper grades 60% Cu in the first tank, 55% Cu in the second and 46% Cu in the third.
operated one copper mine to produce 1,032 t of cement copper
and exported a small quantity of iron pyrites from stock.