Tiberon tables metallurgical study for Nui Phao

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

The study, conducted by Process Research Associates in Vancouver, indicates that about 80% of the contained tungsten in the samples tested is recoverable using a combination of conventional gravity and flotation processing techniques. Tiberon reports that most of the tungsten recovered is in the form of high-grade, low impurity, medium to coarse grained gravity scheelite (CaWO₄).

The metallurgical test were performed on a master composite head sample that was prepared from a quarter split of Nui Phao drill core samples. These samples assayed 0.53% tungsten trioxide, 0.22% copper, 0.28 gram gold per tonne, 0.13% bismuth and 4.1% fluorine (or 8.4% fluorite, CaF₂).

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 about 6-to-10 grams gold per tonne. Tiberon states that 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-to-75% tungsten trioxide with low impurities and a medium grade concentrate averaging 30-to-50% tungsten trioxide. Rejects from this process were then subjected to scheelite flotation from which a third concentrate was produced with grades under 25% tungsten trioxide. Tiberon states that test work is currently underway to improve this final concentrate to in excess of 25% tungsten trioxide. The premium grade concentrates are very low in penalty elements such as phosphorus, molybdenum and arsenic.

The tungsten concentrates can be marketed as is, or can be upgraded to ammonium paratungstate, a higher priced and readily usable tungsten product. This upgrade requires a hydrometallurgical conversion process which Tiberon states will be decided upon only after further product market studies.

Part of the bismuth is recovered as a by-product in the sulphide flotation circuit. This by-product contains about 30% Bismuth and is of a marketable grade. The gold content of the by-product is still pending assay results and additional studies will be made to determine if the bismuth recovery can be enhanced though a separate circuit. Fluorite testing is also underway and to date results have verified that fluorite is recoverable by flotation but concentrate recovery and grades have yet to be refined. Final results are expected by the end of March.

Preliminary plant design flow sheets developed by Laurion Consulting have envisaged a throughput of 1.5 million tonnes per year at a grade of 0.43% tungsten trioxide, or about 5,000 tonnes per year 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 completion in mid March.

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