Gold and silver

Open pit operation

Hualgayoc, Cajamarca

3,800 masl

Started in 2011

Compañía Minera Coimolache S.A. (40.095% BVN) is an affiliate and manage by Buenaventura that produces gold in an open pit operation. The mine which was discovered by Buenaventura, is located in the Districts of Hualgayoc and Chugur, in the Province of Hualgayoc, Region of Cajamarca. It commenced operations in 2011. Buenaventura operates the mine.

Geology: This is a high-sulfidation epithermal deposit with outcropping gold and silver mineralization in oxides, related to silicified breccia associated with a pervasive siliceous alteration. Below the oxides level, there is mineralization consisting predominantly of arsenical copper and, to a lesser extent, covellite and supergene chalcocite. This epithermal event overprints a skarn with retrograde alteration identified at-depth, with clean copper mineralization.

Mining: The mining is performed in two pits in exploitation: Tantahuatay 2 and Ciénaga Norte. The hauling distances to the leach pad and the barren material deposit, in the case of Tantahuatay 2, are 2.4 km and 0.7 km; and in the case of Ciénaga Norte, 9 km and 0.7 km, respectively. The material is loaded using 3-m3 excavators and transported using trucks with a capacity of 20 m3.

Metallurgy: The metallurgical process at Coimolache consists of leaching the ROM ore (obtained from blasting in the open pit) on the leaching heap using cyanide solution. Two processes are carried out in the plant: Merrill-Crowe (zinc precipitation) and ADR (adsorption, desorption, and regeneration using activated carbon). All of the production at Coimolache is turned into doré bars (gold and silver), which are later sold.

Note: As of december 31st of the year indicated.