Arizona Gold & Silver Inc (TSX-V:AZS, OTCQB:AZASF, FRA:A9J0) has reported results from metallurgical test work at its Philadelphia gold-silver project in Mohave County, Arizona, highlighting strong gold recoveries from both agitation leach and heap leach cyanidation testing.
The company said testing was conducted by Kappes, Cassiday & Associates on a 415.5-kilogram bulk sample collected from a fresh bench cut at the project.
Agitation leach cyanidation tests achieved gold recoveries ranging from 91% to 99% across grind sizes between 0.40 millimetres and 0.136 millimetres (40-110 mesh). Cyanide and lime consumption during the tests was reported as low.
Heap leach column testing using high-pressure grinding rolls (HPGR) crushing produced gold recovery of 84% over a 177-day leach cycle. Regression analysis suggested recovery could increase to approximately 86% over a 360-day period, the company said.
Arizona Gold & Silver noted that more than 50% of the total gold recovered during the HPGR column leach testing was extracted within the first 10 days.
The company also reported that HPGR crushing improved gold recovery by an average of 12 percentage points compared with conventional third-stage crushing, while silver recovery increased by about three percentage points.
Silver recoveries ranged from 49% to 72% in agitation leach tests and reached 37% under heap leach conditions.
Agglomeration and compaction testing indicated that heap leach material crushed to 6.3 millimetres was suitable for stacking heights of between 10 and more than 30 metres with the addition of two to four kilograms of cement per tonne during the agglomeration process.
The bulk sample returned gold grades between 1.929 and 1.988 grams per tonne and silver grades between 2.82 and 3.34 grams per tonne. The company noted these grades exceeded the targeted range of 1.0 to 1.2 grams per tonne gold based on previous channel sampling, attributing the difference to the presence of fine and wire-sized gold particles in larger samples.
Arizona Gold & Silver said the results support the potential use of agitation cyanide leaching for higher-grade material containing elevated silver values, while lower-grade material could be processed using heap leaching with HPGR crushing.