Rosemont Copper

Rosemont Ranch is a copper-molybdenum-silver skarn deposit located in Arizona, USA. 

Mining activity in the region dates back to mid 1800s. Production ceased in 1951 after production of about 227,300 tons of ore containing an estimated 17.3 million pounds of copper, 1.1 million pounds of zinc and 180,760 ounces of silver. 

The copper mineralization of the Rosemont deposit is primarily sulfide with a cap of oxide copper mineralization at the surface. The sulfide and oxide ore will be mined through conventional open pit mining techniques. 

Milling rate is of 75,000 tons per day over a mine life of 21 years. 

Sulfide ore will be processed by crushing, grinding, and flotation to produce a copper concentrate and a molybdenum concentrate. The run of mine (ROM) oxide ore will be leached and the resulting leach solution processed through a solvent extraction and electrowinning facility to produce copper cathode.

A positive 2012 feasibility study is based on a 243 million pounds copper per year production plan.

Location

Rosemont Ranch is located in Pima County, Arizona, USA on the northeastern flank of the Santa Rita Mountains approximately 30 miles southeast of the city of Tucson, Arizona. Access would be from State Route 83 at mile 46 and on secondary roads from there. 

Cinnabar, coal, turquoise, clay and pigments were used by Arizona's pre-historic people as early as 1,000 B.C. Native Americans also mined copper and turquoise and made them into jewelry and decorative items. A native silver mine (3,600 pounds silver nuggets) was discovered in 1730s at Arizonac a place that would lend its name to the future American state. American prospectors located and reopened old gold and silver Spanish mines. With the dawn of the 20^th century interest shifted to copper an industrial metal that richly endows the state. 

The 7,284 ha property is located on flat to mountainous topography at elevations ranging from 1,200 m to 2,100 m. 

Climate is dry with most of the precipitation occurring during the wet season July through September.

Geology & Mineralization

The Rosemont deposit is a broad-scale skarn mineralization developed in Paleozoic-aged carbonate sedimentary rocks adjacent to their contact with quartz-latite or quartz-monzonite porphyry intrusive rocks.

Disseminated sulfide mineralization occurs in the Paleozoic units. Weathering has resulted in the oxidation of the sulfides in the overlying Mesozoic units. 

The deposit is typical for the porphyry copper associated deposits of southwestern USA. 

As of July 2012, mineral reserves were estimated at 667 Mt grading 0.44% copper, 0.015% molybdenum and 4.08 g/t silver.

Mining & Operation 

Mining would be through open pit mining methods over a 21 years mine life. Pre-production stripping will be conducted over a 15-month time period. 

The proposed pit operations will be conducted from 50-foot-high benches using large scale equipment. 

Peak mining rates of 318,000 tpd of total material will be realized in Year 1 and 313,000 tpd in Year 2. 

A mining contractor would be in charge of blasting operations as well as storage, mixing and product delivery. Ammonium nitrate and ANFO will be used as explosives. 

Mine personnel would peak at 274 in year 11. 

Sulphide ore would be hauled to the primary crusher while the oxide ore would be transported at the leach pad.

Mine equipment include: Diesel Blasthole Drill, 12.25-in. (2); Electric Blasthole Drill, 12.25-in (1); Drill, Sec/Pioneer, 3.5-in. (Used) (1); Cable Shovel, 70-cu-yd (3); Spare Shovel Dipper (1); Front-End Loader, 36-cu-yd (2); Haulage Truck, 320-ton (24);       Crawler Dozer, D11T-class (2); Crawler Dozer, D10T-class (3); RT Dozer, 834H-class (3); Front-End Loader, 8-cu-yd (1); Excavator, 8-cu-yd (1); Motor Grader, 24H-class (1); Motor Grader, 16H-class (2); Water Truck, 30,000-gal. used (2); Water Truck, 20,000-gal. (1); Fuel and Lube Truck, 50 Ton used (2).

Process 

The sulfide ore will be crushed and ground to a fine size and then processed through mineral flotation circuits (concentrator). 

Copper concentrate will be loaded into highway haul trucks and transported to a concentrate smelter and metal refinery. 

Molybdenum concentrate produced at the concentrator facility will be bagged and loaded onto trucks for shipment to market. 

The run-of-mine oxide ore would be heap leached and copper recovered from pregnant solutions by using SX-EW (solvent extraction-electrowinning) technology to produce high purity copper cathodes. The cathodes would be shipped directly to market. 

A 16 miles 138kV power line is necessary to meet the project's power requirement.

Water would be provided from wells dug into the Santa Cruz Basin which lies 18 miles northwest of the mining project. A 20-inch ductile iron pipe linewould deliver water to the site of the future mine

Environment & Community

Rosemont Copper will inject a total of $19 billion into the Arizona economy over the life of mine, and will create an average of 2,900 jobs annually for the state.

There is some local environmental and political opposition to the development of the Rosemont copper mine. 

Water quantities available to the mining project are limited. 

Permitting for the Rosemont Copper Project involves federal approvals and requires compliance with the National Environmental Policy Act.