Northern Vertex Mining Corp (CVE:NEE) has unveiled metallurgical test results from a low grade bulk sample on its Moss gold-silver mine project in Arizona, saying the gold recovery rate was more rapid for the lower grade material versus the higher grade used in the preliminary economics report.
The column leach test recoveries for the low grade material were 82.7 per cent for gold and 36 per cent for silver, according to the company statement released Friday, with a leach time of 73 days.
This compares with a leach time of 112 days for the higher grade material, which showed recoveries of 84.6 per cent for gold and 76.6 per cent for silver.
The metallurgy was done through a heap leach cyanidation, or column leach, process on mineralized material. Northern said that lower grade material was "readily amenable" to agglomeration - heap leach cyanidation treatment at the 95% -1/4" crush size with respect to gold recovery. It also found that lower cyanide consumption was observed for the low grade material than the higher grade, while a "relatively low" quantity of cement was added during treatment.
The tests, conducted by McClelland Laboratories, used low grade material from the Moss property to determine if there was a relationship between grade and recovery for the higher and lower grade materials.
The company said the sample tested was characteristic of the lower grade material that is expected during pilot plant operations, with construction of this phase now underway.
Yesterday, Northern Vertex provided an update on its construction plans for its Moss gold-silver mine project, saying the first phase of the three-stage development process is progressing on time and on budget.
Last month, the company filed an amended preliminary economics report, with phase II of the project showing an IRR of almost 118 per cent pre-tax and before royalties, and a net present value of US$110 million, at a 5 per cent discount rate. The phase II, or full operation, economics were calculated using gold prices of US$1,500 an ounce and $30 per ounce of silver. The payback period was seen at 15 months, with capex costs estimated at US$26.6 million. Cash costs were projected at just US$490 an ounce.
The company intends to continue with phase I activities, including the evaluation of test mining, heap leach processing and gold and silver recovery. The pilot scale mining and processing will be carried out on about 90,000 tonnes of mineralized rock, at a rate of 1,000 tonnes per day.
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