La Herradura

Overview

Newmont holds a 44 percent ownership interest in the La Herradura gold mining operation, located 250 miles (400 kilometers) south of Mesquite in the northern Mexican state of Sonora. Fresnillo plc owns the remaining interest in the mine and is the operator.

The project consists of 2 properties covering 18,211 hectares.

The mine is in Mexico's Sonora desert. La Herradura comprises an open pit operations with run of mine heap leach processing. It has been in operation since 1998.

La Herradura produced 481,800 ounces of gold in 2011 and gold reserves were estimated at 2.33 million ounces by Dec 31 2011. 

Location

The La Herradura mining operation is located 250 miles (400 kilometers) south of Mesquite in the northern Mexican state of Sonora. It is also 80 kilometers northwest of the city of Caborca and 20 kilometers form the coast of the Gulf of California.

Mexico is a federal constitutional republic located south of the USA. Sonora is one of the 32 Mexican federal entities. Its capital city is Hermosillo.

Some 90% of the state has an arid climate. The Herradura mine site is located in the Altar Desert - part of the larger Sonoran Desert which covers large parts of the Southwestern USA and Northwest Mexico.

Geology & Mineralization

The Herradura gold deposit occurs within a northwest trending belt of Proterozoic metamorphic rocks of greenschist and amphibolite facies and granitoids. The deposit is actually hosted by a quartz-feldspathic gneiss bordered by faults and shear zones.

Gold mineralization is mainly hosted by an en echelon system of quartz veins that dip at low angles. These veins are connected to a thicker set of fault-fill higher grade quartz vein systems believed to represent the feeders for gold mineralization. Mineralizing fluids have a metamorphic origin and were generated during the Laramide orogeny cycle. Vein mineralization is represented by pyrite, galena and sphalerite.

As of December 2011, mineral reserves at Herradura were estimated at 253.2 million tonnes grading 0.71 g/t gold for 2.33 million ounces gold.

Mining & Operation

La Herradura is a conventional truck and shovel open pit mining operation.

Processing

La Herradura consists of an open pit mine with a two-stage crushing and heap leaching facility using a Merrill-Crowe gold recovery circuit.

Most of the run-of-mine is sent directly to a heap leach pad which is insulated by a composite liner of compacted clay and a geomembrane. Cyanide solution is dripped on the pile of rock and pregnant solution collected and processed in a Merrill Crowe plant through a process of clarification, deoxygenation and zinc precipitation.

Environment & Community

Newmont operates in compliance with applicable laws, regulations and other legal requirements. In addition to this mandate, its internal management system includes a global set of performance standards. Its goal is continuous improvement, and it regularly measure itself against these performance criteria to track its progress.

The processing operation is certified by the International Cyanide Management Institute.