well this new technology might improve recoveries considerably
from timberline resources prefeasibility study Talapoosa 2015 it is in sedar dated may
MINERAL PROCESSING AND METALLURGICAL TESTING
A substantial amount of metallurgical test work has been performed over the years on various materials from the Talapoosa deposit. Results from these tests are varied but indicate that the resource materials contained within the PEA pit shell are amenable to conventional cyanide heap leach extraction processes.
Between 1981 and 1999, there were 12 metallurgical test work programs conducted on the Property, by various stakeholders. An additional test program was completed in early 2015 by Gunpoint. In these programs, testing focused mainly on heap leaching. Some work in the 1990s was conducted on agitated leaching, flotation, cyanidation of flotation concentrate, gravity concentration with cyanidation of the gravity tailings and bio-oxidation before cyanidation.
Available metallurgical test work results suggest that conventional heap leaching at a relatively fine crush size is the best approach for processing the materials from Talapoosa. Results from the recent and historic programs provided the basis from which the following estimated heap leach recoveries were used in the development of the PEA. These recovery estimates of three mineralization types were made assuming an agglomerated nominal 1.7 mm (10 mesh) crushed product, generated using high pressure grinding rolls (HPGR) (Table 1.1)
Table 1.1 - Leach Recoveries
Oxidized (HW + FW Type). 77% gold 47% silver
   
Hanging Wall (HW) Type (unoxidized) 65% gold 60% silver
   
Footwall Type unoxidized 59% gold 45% silver
77% 47% 65% 60% 59% 45%
Results from the 2015 test program generally support the earlier heap leach test work. In column tests, both HW and FW-type mineralization within the Bear Creek zones were shown to respond moderately well to simulated heap leach treatment at relatively fine (6.3 mm or finer) feed sizes. Gold recoveries tended to be lower for the Bear Creek FW-type unoxidized material than for the Bear Creek HW-type unoxidized material. Optimization of agglomerating conditions will be required to ensure that the finely crushed material will maintain acceptable permeability during commercial heap leach operations.
Mineralogical examination has shown that gold is frequently present in solid solution with silver as electrum. Metallurgical test work at Talapoosa indicates 50% extraction within 60 days, and 75% extraction within 120 days. These leach cycle times were considered during PEA process development.
All material types tested are sensitive to feed size with respect to gold and silver recovery. In the case of the unoxidized Bear Creek zone HW-type and FW-type material, a portion of the contained gold and silver was also shown to be locked in sulphide mineral grains, or locked in silica. Relatively fine crushing was shown to significantly increase gold and silver recovery.
Testing included evaluation of various feed size reduction equipment. Enhanced gold and silver particle liberation through the use of HPGR resulted in increased recoveries. However, it is unclear whether improvements to recovery were achieved due to the generation of finer particles or from micro-fracturing within particles induced by the HPGR process. |
