Batu Hijau

Overview

Located on the remote island of Sumbawa in the south central portion of the Indonesian archipelago, Batu Hijau is 950 miles (1,528 kilometers) east of Jakarta.

The operation is a joint venture with Nusa Tenggara Mining Corporation of Japan, majority owned by Sumitomo Corporation, and an Indonesian firm, PT Pukuafu Indah. Newmont is the operator and has an ownership interest of 45%.                                                                                                      

The Batu Hijau copper-gold porpyry deposit was discovered in 1990 and began commercial production in 2000. Under the current mine plan, the mine life is predicted to last until 2034.

Batu Hijau is Asia's second largest copper mine.

Location

Batu Hijau is Located on the remote island of Sumbawa in the south central portion of the Indonesian archipelago some 950 miles (1,528 kilometers) east of Jakarta, Indonesia's capital city.

The mine site is 15 kilometers (9 miles) from the company-built port in Benete Bay on the west coast of Sumbawa, 10 kilometers (6 miles) from the south coast of Sumbawa and at an elevation ranging from 300 to 600 meters (985 to 1,970 feet) above sea level. The area is very geologically active with frequent earth quakes.

Geology & Mineralization

The Batu Hijau deposit was discovered in 1990 after 10 years of exploration.

Bata Hijau is a major gold-rich porphyry copper deposit typical of the islands of southeast Asia. These gold-rich porphyries are overwhelmingly hosted by composite stocks of diorite to quartz-diorite and, to a much lesser degree, more felsic compositions such as tonalite and monzogranite.                                                                                                       

The deposits tend to be characterised by a strong correlation between the distribution of copper sulphides (chalcopyrite and bornite) and gold as the native metal in addition to having a notably higher magnetite content. Gold typically occurs as minute (10-15 micron) inclusions in the copper sulphides.

Mining & Operations

The mine occupies 1,320 hectares (3,262 acres) for an open-pit mine, mine processing, support facilities, a town site, a port and other ancillary facilities.

Ore is mined using conventional open pit mining methods. Drilling is carried out utilizing Boart Longyear drill equipment. The blasted
material is loaded into a fleet of Caterpillar 793 haul trucks using a shovel fleet consisting of 6 - P&H 4100A electric mining shovels and  1 P&H 2800XPA shovel. Caterpillar 994 front end loaders are also used in the pit.

In 2011, copper and gold production decreased 48% and 57%, respectively, from the prior year due to lower throughput, grade and recovery as a result of processing more stockpiled material, compared to high grade Phase 5 ore in 2010 and mill down time from motor replacements during the second and third quarters of 2011.

Process 

Following primary crushing, the ore is transported to the concentrator by an overland conveyor, 1.8m wide and 6.8km long. The concentrator circuit consists of two-train SAG and ball mills, followed by primary and scavenger flotation cells, vertical regrind mills and cleaning flotation cells to produce a copper-gold concentrate grading 32% copper and 19.9g/t gold. Counter-current decantation thickeners are used to dewater the concentrate to a slurry, which is pipelined 17.6km from the plant to the port at Benete. Here it is dewatered further, then stocked in an 80,000 t-capacity storage area prior to shipment by sea.                                                                                                       

The tailings from the operation flow by gravity from the process plant to the ocean where they are deposited 3km from the coast at a depth of about 108m. From there, the tailings, which are non-toxic and non-hazardous, migrate towards the Java Trench and are ultimately deposited at depths in excess of 4,000 m.                                                                                                       

The port facilities at Benete bay include a concentrate and general cargo berth, which are fixed, deep water structures, and a pioneer berth which is a shallow water floating structure. Two variable-speed reclaim feeders, fed by two front end loaders, feed a 1,450 TPH 36-inch wide, 1,417-foot long copper concentrate conveyor. The conveyor, located in the copper concentrate building, feeds the shiploader.

Environment & Community

Given that the mine site is characterized by steep terrain and soil that is very susceptible to eroding, the problems of groundwater and storm runoff were paramount during its design and construction. With rainfalls topping 100 inches annually, dams were constructed to control runoff into streams and rivers. There are 13 dams, ranging in size from 26 to 278 feet tall, 7 miles of major drainage canals, and 115 miles of conveyance structures to manage surface water runoff.                                                                                                       

In terms of the mines employees, the company has developed a medical program with medical professionals from International SOS which monitors the health of employees, including their exposure to occupational hazards such as lead, dust, noise and chemicals. Through the program, every job is classified according to the physical job requirements. Medical examinations occur prior to, during and at the conclusion of employment. A comprehensive accident/illness database is maintained. In addition to the skilled medical professionals provided through International SOS, the site employs 24 paramedics working in three first aid posts.                                                                                                       

A significant amount of staff support, time and resources are committed to community relations programs. Batu Hijau targets four major areas for its community development programs: infrastructure, health, education and small business and agricultural business development for 10 neighboring villages and beyond.