Nevada Copper has initiated a definitive feasibility study (DFS) of its Pumpkin Hollow copper project, 8 miles southeast of Yerington, Nevada. Tetra Tech is leading the study, and other consultants may be included in specialist roles for DFS oversight.
Nevada Copper based its decision to proceed to a DFS on the success of its delineation drilling program and substantial progress made in feasibility-related engineering studies. The DFS will evaluate alternative project development options that include a 60,000-st/d integrated open-pit and underground operation and a stand-alone, 7,500-st/d underground high-grade operation. Completion of the DFS is scheduled for mid-year 2011.
Metallurgical testing by G&T Metallurgical Services on composite samples from Pumpkin Hollow’s four ore deposits indicates uncomplicated metallurgy and ores that have a moderate work index. High-grade copper concentrate can be produced at a relatively coarse primary grind. Copper recoveries range from 85% to 94%, depending on the ore deposit. The optimum primary grinds were determined to be P80=150 microns for the North and South deposits and P80=100 microns for the higher-grade East and E2 deposits.
Gold and silver are expected to be recovered to the copper concentrates at levels high enough to receive payment by smelters. The recoveries of these precious metals will vary, depending on the grades in the mill feed.
The primary metallic minerals at Pumpkin Hollow include chalcopyrite, pyrite and magnetite, with magnetite representing 20% to 30% of the total content of three of the four composites. The process flow sheet is conventional, with primary and secondary crushing, SAG and ball milling, and rougher and cleaner copper concentrate flotation and regrind circuits. Use of high-pressure grinding roll technology will be investigated as an alternative to SAG milling for reduced power consumption. Because the E2 and South deposits are higher in pyrite, the facility will also incorporate a pyrite flotation circuit to recover, thicken, filter and ultimately sequester this mineral to reduce acid generation potential.
The final process flow sheet will be finalized once the DFS has established the project scope and phasing of mine development.
Nevada Copper expects to market the Pumpkin Hollow concentrates in the United States and Asia. Transportation options are primarily truck and rail, to West Coast port facilities in the case of export sales. Two possible rail load-out sites are located within 20 road miles of the project site.
Nevada Copper has also initiated a 20,000-m drill program that will focus on the expansion of existing resources, as well as testing several targets on the 22-mi2 Pumpkin Hollow property.