Asiamet reports positive metallurgical test-work results in BKM copper project

By Romel S. Gurky

TSX-listed Asiamet Resources Limited reported on Tuesday positive results from column leach test-work being undertaken as part of the Bankable Feasibility Study on the Beruang Kanan Main (BKM) copper deposit Indonesia?s Central Kalimantan Province.

The company said in a statement that the metallurgical results received to date are in line with previous expectations as outlined in the BKM Preliminary Economic Assessment (PEA). These results will form the basis for the key inputs into the detailed design criteria for the leaching, solvent extraction and electro-winning facilities.

"It is very pleasing to see that the results from the ongoing detailed column leach test-work confirm and support the recoveries and acid consumption predictions from the BKM PEA,? said Peter Bird, CEO of Asiamet in the statement.

?This information will be coupled with the outcomes of the hydrodynamic testing currently in progress and nearing completion, to provide key inputs to the design criteria for the proposed leaching, solvent extraction and electro-winning facilities at BKM. The significant amount of quality data generated from this metallurgical program together with our detailed resource models provides a very solid basis for the mining and process engineering now underway.?

Asiamet said it completed a 122-hole Resource evaluation drilling program, as part of the BKM Feasibility Study. The results of this Resource evaluation were announced on 28 June 2017, with a supporting technical report filed on 15 August 2017. During this program, a number of holes were specifically drilled throughout the BKM deposit to collect representative samples of various material types and grades for detailed metallurgical test-work.

From these samples, six composites were prepared and a total of 20 columns, comprising 12 short columns (2-meter) and 8 long columns (6-meter), were prepared and operated at the CORE Resources laboratory, in Brisbane, Australia. Each composite was tested at two crush sizes (i.e. P80 of 12.5 mm and P80 of 19 mm). Preparatory work ensured the columns were loaded with appropriately agglomerated material and set with suitable bulk density conditions.

After a 200-day leach cycle for the short columns, applying a typical acidic leach solution, the majority of the leachable copper was recovered. The columns were subsequently de-commissioned and the residual material sent for assaying.

All assays have been received for the residual material from the 12 short columns. The detailed diagnostic analytical procedures, including sequential copper assays developed for the BKM mineralization, have allowed for head grades to be verified through mass-balance calculations for each column. These calculations have been utilized to evaluate recoveries of total copper (%CuTot) and soluble copper (%Cusol) for each column.

Copper recoveries from the short column test-work program are in-line with expectations of the BKM Preliminary Economic Assessment (PEA) as announced on 5th April 2016 (85% recovery of the leachable copper) and confirm that the copper minerals in the BKM deposit are amenable to heap leaching. The rates of extraction from the columns suggest optimal soluble copper recovery can be achieved with 3 to 4 kiloliters of solution per ton of ore under leach. Under these conditions the acid consumption characteristics of the ore appear favorable, with little or no acid being consumed.

The soluble copper present in the residual (post-leaching) material was less than 0.1% Cusol for most of the short columns. The sequential copper analysis indicates that the remaining soluble copper within the residual material is predominantly present as slow-leaching covellite, with a higher occurrence in the coarser (+6.75 mm) size fractions.

Based on the leach column performance to-date and supported by preliminary geotechnical and hydrodynamic studies being undertaken currently (HydroGeoSense metallurgical test-work program), the mined ore fed to the heap leach pads will adopt the finer crush size (P80=12.5 mm) as the design criteria for the BKM Copper Project.

The long columns (6-metre) operating at the CORE Resources laboratory were de-commissioned during November, after a 270-day leach cycle. The residual material has been sent for assaying, utilizing the same procedures and protocols that were used for the short columns material. The assay results for the 6-metre columns are expected to be available for analysis early in the New Year. Reporting for this round of metallurgical test-work will follow shortly thereafter. Preliminary interpretations indicate that the leaching performance of the long columns appear consistent with the performance of the short columns.

The leach column test-work provides key design criteria for the leaching, solvent extraction and electro-winning facilities that will be designed as part of the BKM Feasibility Study. An additional round of column test-work will be undertaken, with selected samples already collected from the BKM copper deposit. This further test-work will allow the study team to optimise and refine the metallurgical performance characteristics for the BKM Copper Project. It is expected that the leach columns will be loaded with the selected composites early in the 2018. These columns will run beyond the timeline for the BKM Feasibility Study and form part of the post Feasibility Study detailed engineering design.

The detailed chemical characterization from the leaching test-work program when combined with the hydrodynamic testing program, which is being conducted at the world-leading HydroGeoSense (HGS) facility in Arizona, will provide critical information to support the development of the BKM Feasibility Study and to establish the leach recovery targets for the operation. Metallurgy data generated from both programs will allow the project team to develop a robust and optimized set of design criteria for the heap-leach pads and overall process engineering work.

Editing by Reiner Simanjuntak