An old tailings dam in north-western Queensland may see a new life as a producing gold mine.
In July Diatreme Resources began drilling at the Tick Hill mine, a project abandoned for more than two decades but previously one of Queensland’s most lucrative gold mines.
Drilling results have shown the old tailings dam at Tick Hill has an average grade of 1.12 grams per tonne.
Based on historical records, Diatreme expects the eight hectare tailings dam could contain between 600,000-650,000 tonnes of tailings material.
Drilling around the Tick Hill tenement has also revealed the potential presence of coarse gold, with one sample turning up 43 grams per tonne.
Diatreme CEO Neil McIntyre said the new infill results were extremely encouraging.
“Metallurgical studies are already underway to determine methods to extract the gold contained within the tailings, and will be followed by further studies aimed at determining the quickest pathway to production and unlocking revenue,” he said.
Given the turkey’s nest design of the tailings dam the product, which has already been milled to 70 microns, will be easily excavated and processed.
“It’s straightforward, and it’s all free gold, it was a very unusual deposit,” McIntyre said.
“There were no impurities or nasties attached to the ore, it was very straightforward processing through carbon in leach plant.”
With Tick Hill historically producing some of the highest grade ore in the country at the time, around 24 grams per tonne, extraction techniques did not extend efforts to recovery the last gram or more per tonne, McIntyre explained.
“The recovery rates varied over the years, at the start of the process they weren’t as good as they were in the later years,” he said.
“Given those high grades, they didn’t really pursue the coarse gold that you would normally expect either.”
MacIntyre said Diatreme didn’t target coarse gold specifically, however the clay-lined turkeys nest probably has a sediment of coarse gold, particularly in the area close to the former pump station.
“We deliberately didn’t punch down through the bottom of the tailings dam,” he said.
“There is a clay layer at the bottom, and we wanted to keep the integrity of the tailings dam intact. Our view is that coarse gold, because of its weight, has settled down onto the clay layer.
“That hole where we got it [43g/t sample] we accidently hit the actual wall itself, and then hit the coarse gold, so there’s probably a lining, especially at the southern end of one of the dams which is where the pumps were, there’s a strong likelihood a lot of the gold fell close to the pumps.”