Tiberon tables Nui Phao metallurgical study

Vancouver — Tiberon Minerals (TBR-V) has released positive results from its metallurgical study of the Nui Phao tungsten deposit in northern Vietnam.

The study indicates that about 80% of the contained tungsten in the samples tested is recoverable using gravity and flotation processing. Most of the tungsten recoverable is in the form of high-grade, medium-to-coarse-grained gravity scheelite.

The tests were performed on samples that assayed 0.53% tungsten trioxide, 0.22% copper, 0.28 gram gold per tonne, 0.13% bismuth and 4.1% fluorine.

Once the samples were crushed, the first metallurgical process required the bulk removal of sulphide minerals through flotation. Using this process, a total of 75% of the copper was recovered into a concentrate that assayed 25% copper and contained 6-10 grams gold per tonne. Tests indicate that higher grades of copper concentrate, in excess of 30%, can be produced.

Following the sulphide removal, the samples were subjected to gravity concentration using conventional techniques and equipment. The gravity process liberated two final grades of tungsten concentrates: a high-grade concentrate averaging 65-75% tungsten trioxide with low impurities, and a medium-grade concentrate averaging 30-50% tungsten trioxide. Rejects from this process were then subjected to scheelite flotation from which a third concentrate was produced with grades of under 25% tungsten trioxide.

Ongoing tests are trying to improve this final concentrate to more than 25% tungsten trioxide. The premium-grade concentrates are low in penalty elements such as phosphorus, molybdenum and arsenic.

The tungsten concentrates can be marketed as is, or upgraded to ammonium paratungstate, a higher-priced and readily usable tungsten product.

Part of the bismuth is recovered as a byproduct in the sulphide flotation circuit. This byproduct contains about 30% bismuth and is of a marketable grade. The gold content of the byproduct has yet to be determined, and additional studies will be made to determine if the bismuth recovery can be enhanced through a separate circuit. Fluorite testing is also under way. To date, results have verified that fluorite is recoverable by flotation, though concentrate recovery and grades have yet to be refined. Final results are expected by the end of March.

Preliminary flow sheets call for throughput of 1.5 million tonnes per year at a grade of 0.43% tungsten trioxide, or, again annually, about 5,000 tonnes of contained tungsten trioxide in all three concentrates. The projected tungsten distribution in the three concentrates are 63% tungsten trioxide in the premium-grade gravity product, 19% contained tungsten trioxide in the medium-grade gravity product and 18% contained tungsten trioxide in the low-grade flotation product.

The current indicated resource at Nui Phao stands at 12.3 million tonnes grading 0.43% tungsten trioxide, 0.31 gram gold, 0.26% copper and 0.12% bismuth. In addition, 10.2 million tonnes grading 0.47% tungsten trioxide, 0.26 gram gold, 0.27% copper and 0.13% bismuth were placed in the inferred resource category. The resource was based on tungsten trioxide only, using a cutoff grade of 0.25% tungsten trioxide on the first 70 holes. Data from an additional 33 holes and the secondary credit resources will be included in an updated resource calculation, scheduled for mid-March.

Tiberon holds a 70% interest in the Nui Phao project, with the remainder held by Vietnamese parties.