Unigold Inc. is pleased to announce initial and positive metallurgical test results from the Candelones Extension, Neita Project in the Dominican Republic.
The initial metallurgical test results demonstrate:
- gold, silver and base metal recoveries of 85-90% to a 'clean' sulphide concentrate
- a sulphidic concentrate at 12% of the mass
- multiple final processing solutions or concentrate sale are open to the Company.
"These positive and initial metallurgical results are an important milestone for the company," commented Andrew Cheatle, President and Chief Executive Officer. "They clearly demonstrate that the gold and other metals can be recovered to industry standards and by proven technologies. These results address a key risk and provide an opportunity for our flagship project."
Metallurgical Test Work Details
20 metallurgical samples (half core) totalling 188 kilograms were taken from the 2011/2012 drilling program at Candelones Extension representing typical lithologies from the mineralized zone and ranging in grades to provide a master composite and variability samples. The samples were shipped to G&T Metallurgical Services Ltd. (part of ALS Metallurgy "ALS"), Kamloops, Canada: an independent metallurgical test facility where all test work was performed. Upon arrival at ALS, the samples were composited into a sample deemed to be representative of the deposit.
The objective of the flotation test work was to produce a bulk gold, silver, copper-zinc concentrate that would be suitable for on-site processing and also to meet the specifications of conventional smelters. The metallurgical composites were used in number of initial batch tests to define preliminary process criteria such as reagent consumption, grind size and flotation grade/recovery relationships.
The ALS work focused on the production of a flotation concentrate, which is a very common procedure for sulphidic refractory gold ores. This was achieved for the Candelones Extension sample, with 85-90% of the gold, silver and base metals recovered into a flotation concentrate, at 12% of the mass. A simple comminution, flotation circuit is envisaged, followed by a treatment route for the concentrate.
Future work needs to evaluate the optimum grind size and to attempt to increase it as far as possible to reduce the grinding circuit capital and operating costs. However, these initial tests suggest a much coarser primary grind might be possible and a simple SAG mill circuit plus cone crushers could be considered.
These options could include, at site:
- Pressure Oxidation. Results of the POX test were encouraging, with about 95% gold dissolution in 24 hours.
- Intensive cyanidation.
- Albion Process (as is being currently commissioned on another DR project).
- Roasting, with a view to recovering both precious and base metals.
- Production of differential flotation concentrates, i.e. a copper concentrate (for sale) and a pyrite concentrate (for treatment or sale). One preliminary test gave some encouragement with a 17% Cu concentrate and this line of investigation will be continued.
- Sale of the bulk concentrates to third parties, or a smelter.
The gold content in the feed for the master composite was estimated at 1.5 g/t and the gold content of the variability samples varied between 0.3 and 6.1 g/t. The total sulphide mineral content, in the master composite, accounted for approximately 13.5 percent of the sample mass (S was 6.8 percent). The majority of sulphide minerals present, in order of abundance, were: pyrite, sphalerite and chalcopyrite. Approximately 12.5 percent of the sulphide mineral was present as pyrite. Other key chemical content of the master composite sample were: silver (7 g/t), copper (0.12%), zinc (0.45%), and arsenic (0.019%). The rock was described as "moderately hard."
With these results Unigold is now in the position to move ahead on more detailed metallurgical studies, and these will be completed in 2013.
John A. Wells, M.A. Sc., an independent metallurgical consultant, was retained by Unigold to oversee the initial test work at ALS and to provide an initial conceptual level flow sheet together with an independent assessment of the gold, silver, copper and zinc recovery. Mr. Wells has extensive industry experience in minerals processing, particularly in the recovery of gold and silver. He has held senior positions in head office consulting, project development and operations with Goldfields Limited, AngloGold Ashanti and Barrick Gold Corporation. Mr. Wells is a Qualified Person for the metallurgical test work at Neita under the definitions established by National Instrument 43-101.