Aquiline Resources Inc. announced the results of the metallurgical program performed on the Loma de La Plata zone of the Navidad silver project by Xstrata Process Support (”XPS”) of Sudbury, Ontario. This program commenced in the first quarter of 2008, and was performed to corroborate and expand upon the metallurgical program results obtained by G & T Metallurgical Services Ltd. (”G & T”) which was announced in the second quarter of 2008. Results obtained by XPS support those of G & T in demonstrating that a low mass, high grade silver concentrate can be produced. Rougher concentrates containing up to 39 kilograms of silver per tonne at 85% – 95% recoveries were achieved using simple crushing, grinding and flotation circuits. The final report will be filed on SEDAR and posted to the Company website at www.aquiline.com.
Individual samples from 19 diamond drill holes weighing approximately 1,070 kilograms were selected by XPS to develop six variability composites and two main composites on two geometallurgical units defined as the Sulphide and the Oxide zone. Most of the known ore at Loma de La Plata is characterized as low sulphide ore contained in the Sulphide zone, hosted by latites, although the southwest portion of the zone (Oxide zone) is exposed on surface and shows signs of oxidation. The six variability composites were tested to determine open circuit rougher concentrate recoveries and mineralogical characterization, while the two main composites (one Oxide and one Sulphide) were tested for bond work index determination, Falcon Concentrator work, cyanidation testing, reagent exploration and exploratory cleaner tests. No locked cycle tests were performed in this program. This assessment would be considered as Scoping Level.
The head grades of the six variability composites and two main composites are contained in the report filed on the website at www.aquiline.com. A table summarizing these results accompanies this press release.
The following results have been achieved:
- Overall rougher flotation test silver recoveries ranged from 85% – 95%, which is higher than the range of recoveries obtained in the G & T testing, which ranged from 80% – 85%.
- The silver content in the 1st rougher concentrates varied from 2.4 to 39.3 kilograms of silver per tonne of concentrate. Exploratory cleaner tests at XPS achieved concentrate grades consistent with G&T results, (approximately 50 kg/t) albeit at lower overall recoveries. More extensive cleaner testwork at XPS will commence shortly.
- Generally, oxide samples demonstrated lower silver recoveries than the sulphide samples, but higher silver concentrate grades.
- Combined copper and lead values in the rougher concentrate were typically between 10 – 20%, which is similar to the range obtained by G & T.
- Mineralogical analysis indicates that acanthite is the main silver carrier in both the Sulphide and Oxide zones, with stromeyerite being less common, but contributing up to 15% of the total silver deportment.
- Arsenic and antimony levels are most commonly associated with silver bearing tetrahedrite or tennantite, but remain below levels that would typically attract smelter penalties.
- No assays were performed for cadmium, which the G & T results found to be present in the single composite tested for cadmium. However, cadmium was reported as less than 200 g/t in the concentrate, which is considered to be below levels likely to present any concern to smelters.
- Cyanide leaching tests demonstrated silver recoveries ranging from 77.2% to 98.5%, with results strongly correlated to particle size and cyanide concentration in solution.
- A standard Bond Ball Mill work index of 18.2 kWh/ tonne for the Sulphide main composite and 18.9 kWh/tonne for the Oxide main composite was achieved, which XPS interprets as relatively hard.
Damian Spring, Chief Mining Engineer for Navidad, commented “The metallurgy results from XPS are positive, and confirm the high recoveries obtained by G & T in their testing. We are on track to release our scoping study on Loma de La Plata in September, which will give stakeholders a benchmark for the economics that can be obtained by developing Navidad in a phased approach.”
The Loma de La Plata zone is estimated to contain 9.1 million tonnes (indicated) at average grades of 226 g/t Ag, or 66 million contained ounces Ag plus 17.3 million tonnes (inferred) at average grades of 159 g./t Ag, or 89 million contained ounces Ag (Snowden Mining Industry Consultants, December, 2007). The average depth of the mineralization has been within 200 metres of surface over a surface area approaching 39 hectares, which is still being expanded with further drilling. The Company is focusing on the development of a simple but pragmatic process flow sheet as a precursor to a Feasibility Study, depending on financing and permitting conditions.
Next Phase Metallurgy Testing
The next stage of test work will include additional bench scale testwork on new Loma de La Plata samples, as well as on samples collected from zones adjacent to Loma, which appear to have similar characteristics. Samples for a pilot plant program are also being collected in a new drilling campaign at Loma de La Plata anticipated to commence in the fourth quarter of 2008.