Minto project approaches startup

Sometimes less can be more.

That's what Sherwood Copper Corp. is finding with metallurgical tests it is conducting on ore samples from the Minto project north of Whitehorse in the Yukon Territory.

Minto is an advanced-stage copper-gold project with reserves exceeding 356 million pounds of high-grade copper and geology that indicates significant exploration potential. Development of an open pit mining operation with conventional crushing, grinding and flotation to produce copper concentrates with significant gold and silver credits is well under way with pre-stripping and construction work.

Sherwood expects to export the concentrates via the Skagway Ore Terminal in Skagway, Alaska, to smelters in Asia for treatment and sale.

Escalating fuel, labor and equipment costs over the past two years have pushed the total estimated capital cost of the project up to C$90 million. Production is on track to begin in the second quarter of 2007.

Over the life of the Minto project, Sherwood expects to produce 300 million pounds of copper, 122,000 ounces of gold and 1.8 million ounces of silver.

Coarser grind could cut costs

The Vancouver-based junior announced encouraging results in November from tests using a coarser grind for processing high-grade copper-gold ore at Minto. A coarser grind could reduce operating costs and increase mill throughput.

Sherwood President and CEO Stephen Quin said the tests, conducted by G&T Metallurgical Services, suggest that a coarser primary grind in the mill at Minto with a regrind of the concentrates might achieve high copper and gold recoveries and similar concentrate grades to those assumed in the feasibility study that the company completed this summer.

"This approach could reduce operating costs," Quin said in a statement.

The tests were based on three composites prepared from core samples collected from three different areas within the main Minto pit. A series of batch rougher and cleaner tests indicated that the samples could be successfully processed through the rougher circuit at a nominal primary grind size of 80 percent passing a 300-micron grind size.

That is double the 150-micron grind assumed in Sherwood's feasibility study, but the process would require regrinding the rougher concentrate to 80 percent passing 70 microns, Sherwood said. Under those batch conditions, 95 percent of the copper and 72 percent of the gold was recovered into a concentrate containing 40 percent copper.

Using a coarser primary grind and a regrind of the concentrates would be less energy intensive and would reduce operating costs, the company said.

Operating conditions simulated

Additional locked-cycle tests simulating operating conditions were carried out on a range of primary grind sizes from 80 percent passing 200 microns to 80 percent passing 300 microns, and a regrind of the concentrates ranging from 80 percent passing 30 microns to 80 percent passing 56 microns, and achieved similar results to the batch tests.

On average, 95 percent of the copper and 78 percent of the gold was recovered into a concentrate grading 43 percent copper, Sherwood said.

Included in the locked-cycle tests were gravity concentration tests on the rougher tails to see if any incremental gold could be recovered. These tests indicated that some additional gold, up to 8 percent on one test, could be recovered from the rougher tails, the company said.

Sherwood said it will conduct more tests to confirm the results, using a primary grind of 80 percent passing 300 microns and a concentrate regrind of 80 percent passing 70 microns, as recommended by G&T Metallurgical, with continued evaluation of a gravity circuit to incrementally improve gold recoveries.

If the results are confirmed, the additional tests would form the basis of a decision to adjust the base operating conditions for the mill when operations commence, the officials added.

More exploration in 2007

In early December, Sherwood announced encouraging drilling results from its 2006 exploration of Area 2, a significant ore zone adjacent to the main Minto deposit.

Quin said the drill holes returned significant sections of greater than 2 percent copper and 0.5 grams per ton of gold.

"The high grades over substantial thicknesses in drill holes 06SWC-111, -125 and -132 are particularly encouraging as they are the first assay results from the bornite-rich area we were following late in the 2006 drill program," he said. "By tracing this mineralization to the northwest, we ended up extending high grade copper-gold mineralization well outside the limits of our initial target area. We plan to complete a resource estimate and pre-feasibility study with the objective of converting resources defined in Area 2 to mineral reserves, ideally before we commence production in 2007."

Sherwood also announced completion of a gradient induced polarization survey conducted over 797,000 acres south of the main deposit encompassing Area 2. Aurora Geosciences Ltd. of Whitehorse conducted the IP survey.

"The results of the recently completed IP survey are very encouraging: when we compare the signature and aerial extent of newly defined geophysical anomalies with the signature of Area 2, we see excellent opportunities for further discoveries of near surface, high-grade copper-gold mineralization," Quin said. "We aim to be testing both previously known but now better defined targets as well as the newly defined ones in 2007 and look forward to an exciting exploration season."