Nova affirms Korbel ore sorting viability
Most of the gold is in sheeted veins easily detected with XRT North of 60 Mining News – March 19, 2021
Last updated 3/18/2021 at 5:12pm
Nova Minerals Ltd. March 15 said it is encouraged by the results from ore sorting tests completed on material sourced from the Korbel Main deposit on its Estelle gold project in Alaska.
According to the most recent calculation, Korbel Main hosts 3.28 million ounces of gold in 291 million metric tons of Australian Joint Ore Reserves Committee- (JORC) compliant inferred resource averaging 0.35 grams per metric ton gold. This resource is expected to be expanded with a new calculation completed by mid-year.
Nova has been testing ore sorting as a means of increasing the grade of material processed through the mill and recovery circuit in a future mine at Korbel.
This round of tests utilized dual-energy x-ray transmission (DE-XRT) ore sorting technology. In the case of Korbel, the XRT sensors identify rocks with arsenopyrite that carries most of the gold. Previous bulk sorting studies carried out by ABH Engineering shows that gold at Korbel is not evenly dispersed through the rock.
"This deposit has a majority of its gold contained in discrete high-grade sheeted vein rocks which are easily concentrated with existing DE-XRT ore sorting technologies," said Brent Hilscher, vice president mineral processing at ABH Engineering and the lead for Nova's ore sorting study. "Once concentrated, we have several options to achieve higher gold recovery at a very low overall cost."
Roughly 1,176 kilograms (2,593 pounds) of material from holes KBDH-005 and KBDH-025, which were drilled into the newly discovered Southeast Extension of the Korbel Main deposit, was shipped to TOMRA's testing facility in Australia.
After blending the material from these two holes together, TOMRA split the sample into two equal sub-samples, each weighing 588 kg (1,296 lb). One sample was used for the current study, the other was reserved for future follow-up testing.
The tested sample, which averaged 0.67 g/t gold, was run through the XRT sorter in three stages. During the first stage, the sorting machine upgraded the material to 6.1 g/t gold in about 4% of the original mass but only captured around 36% of the total gold in the sample. During the second run, the grade was 3.4 g/t gold in about 15% of the original mass while capturing 74% of the gold. During the third run, the grade was 2.1 g/t gold in 26% of the original mass while capturing 82% of the gold. During the final run, the grade was 1.3 g/t gold in 46% of the original mass while capturing 90% of the gold.
By the fourth stage, the XRT sorter had picked out almost all material with arsenopyrite mineralization, leaving about 0.12 g/t in the 54% of the material rejected as waste.
"Significant increases in mine productivity could be achieved through the rejection of a considerable proportion of lower grade rock before processing," said Nova Minerals CEO Christopher Gerteisen. "By using an XRT sort, we would prospectively reduce the volume of ore and lift the grade appreciably, rejecting lower grade material ahead of the milling and processing circuit. This would minimize energy requirements, tailings generation, and would lower processing costs overall."
Nova says the results of this testing confirm the viability for XRT ore sorting to be included in an upcoming scoping study for Korbel.
By concentrating the highest-grade rocks into a relatively small mass, Nova says it can create a high-value material that is suited for high recovery extraction through to cyanidation. This method is expected to reduce costs and increase gold production.
"This provides Nova with the opportunity to operate at a lower cut-off grade, and potentially increase the ounce per annum profile of the project, said Gerteisen. "By utilizing ore sorting, and increasing production efficiency through this now proven and increasingly used technology, Nova's environmental footprint could also be reduced, in line with our ESG strategy."