Challenger Gold (ASX: CEL) has been buoyed by impressive new results from metallurgical testwork at Hualilan gold project in San Juan, Argentina.
Recently completed metallurgical testwork re-examining cyanide leaching technology on Hualilan mineralisation has indicated high gold recoveries of up to 89.3%, with sodium cyanide consumption at 0.7 kg/t.
This was a dramatic upgrade to historical recoveries (<40%) for gold and silver, with high cyanide consumption.
New metallurgical examination
The recently completed testwork indicated high recoveries for both gold and silver in new examination into the use of cyanide leaching technology on Hualilan mineralisation.
The metallurgical program is considered a key plank as Challenger progresses with an update on a scoping study for a 2.8 million ounce gold project.
The scoping study is initially evaluating the commercial potential of Hualilan’s high-grade core of mineralisation made up of 8.5 million at 5.4 grams per tonne gold equivalent (4.8 g/t gold, 14.2 g/t silver, 1.6% zinc and 0.14% lead) at a 2.3 grams per tonne gold equivalent (AuEq) cut-off.
The testwork conducted by leading metallurgical laboratory SGS Lakefield in Canada demonstrated excellent recoveries of gold and silver using traditional sodium cyanide leaching. This testwork was conducted using a master composite, designed to be representative of the in-pit component of the Hualilan Mineral Resource Estimate.
Managing director, Kris Knauer, said Challenger elected to further confirm the initial positive results with follow-up studies immediately undertaken at the highly-regarded Base Met Lab in Canada.
That confirmatory testwork also achieved recoveries of 89% for gold and 71% for silver.
“Hualilan has the ability to continually surprise on the upside. A program of metallurgical testwork conducted, really, for completeness, has the potential to change the way Hualilan is developed,” Mr Knauer said.
“Initial trade-off work indicates that the outcome between developing Hualilan via flotation compared to CIL needs to be properly evaluated in the Scoping Study. CIL offers several advantages including; production and sale of s gold and silver doré, lower up-front capital, higher payabilities and simplification of the flow sheet and logistics.”
“Additionally, the ability to use CIL offers a number of benefits such a likely perceived lower overall project risk profile and a broadening of the potential investor/finance base for the company,” he added.
Sodium cyanide leach testing
An initial series of sodium cyanide leach testwork was undertaken at SGS Lakefield to rule out process routes, other than gravity and flotation, as viable options for the Hualilan Gold Project.
The testwork demonstrated recoveries of 89.3% for gold and 46.1% for silver at a coarse grind of 100 μm (P80) and a relatively low cyanide consumption of 0.7 kg/t.
The subsequent repeated and expanded sodium cyanide leach testwork panel at the Base Met Lab tested a sample that had an average core sample assay grade of 1.06 g/t gold and 6.60 g/t silver.
This testwork produced similar results producing recoveries of 88.6% for gold and 70.7% for silver.
Column tests underway
Challenger is currently conducting a column test, with early results exceeding expectations.
A second column test has been initiated to demonstrate that the results of the first column test were reproducible and not a result of one-off variability.
Challenger says that while the initial Column test results have been positive, a more comprehensive program of column testwork will need to be undertaken before definitive conclusions on the possible viability of heap leach as a processing route for Hualilan can be drawn.
This program of 13 column tests includes: ~0.2 g/t gold, ~0.4 g/t gold, ~0.6 g/t gold, ~0.8 g/t gold and ~1.0 g/t gold for Sediment-hosted and Intrusion-hosted mineralisation, which makes up the majority of the potential low-grade feed material by mass; and, ~0.2 g/t gold, ~0.4 g/t gold and ~1.0 g/t gold for the Skarn-hosted mineralisation.
Results for this program are expected to be available around the end of October 2023.
