Lancaster County, South Carolina, US
Two million ounce (Moz)
Romarco is developing the Haile open-pit gold mine in Lancaster County, South Carolina, US. Feasibility study of the gold mining project was completed in February 2011. Construction was started in May 2015 and first gold is expected to be poured in the fourth quarter of 2016. The project is expected to generate approximately 500 construction and 300 production jobs.
The mine is expected to have a mill throughput of 7,000t / d during its mine life of more than 13 years. It is estimated to produce 172,000oz of gold in the first year and an average of 150,000oz a year during the first five years.
Haile gold mine location, history, geology and mineralisation
Betze-Post gold mine, in Nevada, US, is the eighth deepest open-pit mine in the world.
The mine was discovered in 1827 by Benjamin Haile and operated for approximately 200 years. The north central portion of South Carolina is geologically situated in the Carolina superterrane or Carolinia.
The Haile gold mine is located within the Carolina terrane, which was formerly known as the Carolina slate belt, a unique geologic feature trending from Georgia to Virginia. The gold mineralisation occurs along a trend of moderately-to-steeply dipping ore bodies within a regional corridor running from the west-southwest (WSW) to the east-northeast (ENE).
Most of the gold mineralisation is disseminated and occurs in silica-rich, pyrite-pyrrhotite-bearing metasediments. Quartz is dominant, pyrite is subordinate and sericite is variable within the mineralised zones. Quartz and pyrite are abundantly available at the centre of the mineralised zones, whereas sericite is minimal.
Haile gold mine reserves
The proven and probable gold reserves in the Haile gold mine are estimated to be 30.5Mt at 2.06g / t Au. The mine is estimated to contain two million ounces of gold.
Mining at the Haile gold deposit
Conventional open-pit mining methods, involving drilling and blasting, will be applied at the Haile gold mine. The initial mining fleet is expected to comprise 12 Cat777F haul trucks, two front-end loaders, one hydraulic front shovel, and other support equipment.
The mine is expected to produce 2.55Mt of ore a year, which will be delivered to the 7,000t / d processing plant.
Ore processing at Haile
The run-of-mine (ROM) ore will be initially crushed in a primary jaw crusher and stockpiled before being conveyed to the semi-autogenous grind (SAG) mill.
The SAG mill will operate in closed-circuit with a vibrating discharge screen and a pebble return circuit, while the ball mill will operate in closed-circuit with hydrocyclones to produce the desired grinding product size of 80%.
A portion of the load circulating in the grinding circuit will be treated in a flash flotation cell, while the concentrate will go to a regrind circuit and the remaining portion will be sent to the flotation circuit that uses rougher flotation. The flash and rougher flotation concentrate will be combined to achieve a grinding product size of 80% passing 13 microns.
The reground concentrate will be thickened prior to cyanide leaching in agitated leach tanks. The concentrate leach discharge will be processed in a carbon-in-leach (CIL) circuit to dissolve gold and silver contained in the slurry and adsorb the dissolved metals from the solution onto activated carbon.
Tailings from the flotation circuit will be thickened in order to recycle water to the grinding circuit. The thickened tails will be combined with the leached concentrate and processed in a CIL circuit to dissolve gold and silver.
Loaded carbon from the CIL circuit will be removed by acid washing, and stripped with hot caustic-cyanide solution. Precious metals from the concentrate will be recovered by electro-winning method, and the resultant sludge will be mixed with fluxes and melted to produce gold-silver doré bars.
On 29 May 2015, Romarco obtained a $200m senior secured project finance facility for Haile with no mandatory gold hedging. The loan facility is provided by Caterpillar Financial Services, ING Capital, Macquarie Bank, and Société Générale Corporate & Investment Banking.
Infrastructure facilities at the Haile gold mine
Power supply will be provided from the Lynches River’s 69kV transmission grid. A new 5mi-long, 69kV power line will be constructed to connect the main HGM substation with the grid.
Key players involved
M3 Engineering & Technology (M3) prepared the feasibility study for the project, with the participation and contribution of Independent Mining Consultants (IMC) and AMEC Americas (AMEC).