Integra Resources has reported the results of a preliminary economic assessment (PEA) of its DeLamar gold-silver project in southwest Idaho that supports project development. Initial mine life is planned at 10 years, producing total payable production of 1.03 million ounces (oz) of gold and 16.6 million oz of silver. 

Production would derive from open-pit mining of the DeLamar and Florida Mountain deposits, which are located on adjacent properties within the project.

Processing would include both heap leaching of oxide and transitional mineralization and milling of unoxidized mineralization from the Florida Mountain deposit. The heap-leach processing rate is targeted at 27,000 metric tons per day (mt/d) throughout the 10-year mine life. A 2,000-mt/d mill would come into production during the third year of production.

Production during years two through six of operations is forecast at 126,000 oz per year (oz/y) of gold and 1.8 million oz/y of silver.

The life-of-mine open-pit strip ratio is estimated at 1.09:1, waste to ore.

Preproduction capital expenditures to develop the project are estimated at $161 million. Life-of-mine all-in sustaining costs of production are estimated at $619/oz of gold net of by-product silver production.

The after-tax payback period is estimated at 2.4 years.

Integra contemplates conducting open-pit mining at the DeLamar and Florida Mountain deposits using an owner-operated, conventional mine fleet that will include production drill rigs, 23-m3 hydraulic shovels and 12.8-m3 front-end loaders, and 136-mt haul trucks. Mining will begin at Florida Mountain with heap leach material followed by a mix of heap leach and millable materials. Beginning in year six, heap leach material will transition from the Florida Mountain area to the DeLamar mining area.

Florida Mountain oxide and transitional mineralization will be crushed to 50 mm, conveyor stacked onto a heap leach pad, and leached using a low-concentration sodium cyanide solution. Pregnant solution will be processed in a Merrill-Crowe recovery plant, where gold and silver will be precipitated and doré will be produced.

DeLamar oxide and transitional mineralization will be crushed to 13 mm, agglomerated, conveyor stacked onto a heap leach pad, and leached using a low-concentration sodium cyanide solution. Pregnant solution from the DeLamar heap leach will be processed in the Merrill-Crowe recovery plant, where gold and silver will be precipitated and doré will be produced.

Mill processing will incorporate crushing/grinding, gravity concentration, flotation, concentrate fine regrinding, and final concentrate agitated cyanide leaching.

Integra President and CEO George Salamis said, “This PEA is simply a starting point for us in terms of further value enhancement to come in the near-term. A large portion of the DeLamar unoxidized resource has been excluded from this study, and there remain substantial undrilled areas with upside potential for oxide and transitional gold-silver mineralization along the margins of the current DeLamar and Florida Mountain resources that are completely open for resource expansion.