Tiberon’s Nui Phao enters feasibility stage

Vancouver — Armed with $3 million in financing, Tiberon Minerals (TBR-T) is proceeding with a bankable feasibility study of its 70%-held Nui Phao tungsten project in Vietnam.

Since 2000, the junior has been drilling on the property in an attempt to prove up a large open-pit deposit. The results were included in a prefeasibility study which proposes a conventional truck-and-loader open-pit mine operating at 10,000 tonnes per day over a life of 16 years. The single open pit is expected to have an overall stripping ratio of 1.6 tonnes of waste to one tonne of ore.

Based on an initial capital cost of US$140 million and annual throughput of 3.5 million tonnes per year, Nui Phao would generate a 21% internal rate of return. The payback period would be 3.8 years, and the average annual production of concentrates is estimated at 6,000 tonnes tungsten trioxide, 196,000 tonnes fluorite, 5,600 tonnes copper, 5,000 oz. gold, and 360 tonnes bismuth.

The project’s net present value (NPV), after tax, is US$338 million, based on a 0% discount rate. At a 10% discount rate, the NPV falls to US$88 million.

Commodity prices for the study are based on long-term historical prices of US$5,475 per tonne for tungsten trioxide, US$140 per tonne for fluorite, US85 per lb. for copper, US$325 per oz. for gold, and US$3.20 per lb. for bismuth.

The process plant would employ a conventional “gravity plus flotation” tungsten concentrator. Preliminary metallurgical tests indicate recoveries of 80% tungsten, 70% fluorite, 75% copper, 20% gold and 10% bismuth.

The plant would consist of a conventional, 3-stage crushing circuit, ore storage, grinding, sulphide and copper flotation, gravity concentration of tungsten, tungsten and fluorite flotation, and storage of concentrates.

Anticipated direct costs are as follows:

— US$12.7 million for the mine;

— US$51.2 million for the process plant;

— US$6.5 million for utilities;

— US$4.4 million for site preparation and roads;

— US$3.6 million for tailings;

— US$3.4 million for ancillary facilities.

Indirect costs are pegged at US$39 million, and contingency costs add US$18.9 million to the bill.

At last count, the measured resource at Nui Phao consisted of 27.1 million tonnes averaging 0.68% tungsten trioxide-equivalent, or 0.25% tungsten trioxide, 0.25 gram gold per tonne, 0.23% copper, 0.11% bismuth and 8.2% fluorite. The calculation was based on a cutoff grade of 0.2% tungsten trioxide-equivalent.

The indicated resource is pegged at 22.3 million tonnes averaging 0.6% tungsten trioxide-equivalent, or 0.19% tungsten trioxide, 0.22 gram gold, 0.21% copper, 0.104% bismuth and 7.9% fluorite. The inferred resource is pegged at 24 million tonnes averaging 0.55% tungsten trioxide-equivalent, or 0.18% tungsten trioxide, 0.16 gram gold, 0.16% copper, 0.081% bismuth and 8.1% fluorite. The resource estimates included all drill holes up to and including no. 110.

Over the past six months, Tiberon has been attempting to enhance the economics of the Nui Phao project by outlining additional resources and improving fluorite recovery and bismuth recovery for a sulphide concentrate.

The final results of the 2003 drill program are promising. Holes 147 through to 155 were collared along the northwestern edge of the deposit, returning up to 0.41% tungsten trioxide, 0.13 gram gold, 0.22% copper, 0.03% bismuth and 23.3% fluorite over 6.1 metres in hole 154.

Hole 147 was drilled in the southwestern section and yielded 0.21% tungsten trioxide, 0.12 gram gold, 0.03% copper. 0.02% bismuth and 10.7% fluorite over 143 metres.

Hole 155 — a stepout hole drilled on the northern portion of the Nui Phao North Deposit, some 1 km northeast of the main deposit — returned no significant values.

Now that the program is complete, the Calgary-based company has hired Engineering firm AMEC E&C Services to calculate a new resource estimate.

The company recently reported positive results from a metallurgical study designed to enhance the bismuth recovery. The results show a bismuth recovery exceeding 50%, achieved through a combination of conventional flotation and hydrometallurgical processing.

The feed samples were first subjected to flotation tests to produce an intermediate copper-bismuth concentrate, which assayed 1% bismuth and 3% copper. The concentrate contained 55-60% of the bismuth and 84-87% of the copper. The product was then leached for bismuth using sulphuric acid and sodium chloride. Leaching for one hour at room temperature and at atmospheric pressure resulted in the extraction of about 95% of the bismuth in the leach feed, equivalent to more than half of the bismuth contained in the overall head sample. Loss of copper into the leach solutions ranged from less than 0.1% to 0.3%.

The tests indicated that the recovery of bismuth from leach solutions by conventional cementation on iron shavings produced a bismuth sponge assaying 40-60% bismuth at a recovery exceeding 99%.

The company says it will investigate electrowinning as a possible alternative to cementation, as electrowinning might produce a higher-grade bismuth metal and simplify commercial application.

The bankable feasibility study will entail engineering, pilot-plant metallurgical studies, geotechnical studies, and an environmental impact assessment.

The $3-million financing consists of a private placement of 1.4 million units priced at $2.20 a piece, A unit contains one share and half a warrant. A full warrant allows the holder to acquire one share of Tiberon at $2.70 for two years.