Key Highlights

•  Assays for 2,161 samples from old diamond core and reverse circulation chips returned gold, including 3m at 2g/t from 99m in hole BRD018 and 6m at 1.1g/t from 155m in BRD012.

•  The company says earlier drilling often skipped the oxide zone, and the results with its own drilling suggest gold along a corridor of about 1.9km.

•  Results are downhole widths, no resource is defined, and a 21-hole RC campaign awaits assays alongside a planned 3,000m RC programme.

Australian Gold and Copper (ASX:AGC) has reported gold in historical drill core and chips that were never fully sampled, at its Browns Reef Project in central New South Wales. The company has received assays for 2,161 samples taken from old diamond core and reverse circulation (RC) chips held from earlier drilling by other explorers.

The work focused on the oxide zone, the weathered near-surface portion of the rock that previous explorers often skipped. The company argues that this gap left potential gold mineralisation untested.

What the historical holes returned

Hole BRD018, drilled by Eastern Metals in 2022, returned 3m at 2g/t gold from 99m in oxide material, including 1m at 4.2g/t gold from 100m.

Hole BRD012, drilled by Kidman Resources in 2014, intersected 6m at 1.1g/t gold from 155m, including 1m at 2.3g/t gold from 157m. This hole lies about 300m south of the area AGC has been drilling at the Evergreen prospect.

All reported widths are downhole, and true widths are not yet known.

Why the oxide zone was overlooked

The company explained that many early diamond holes in the area were started with roller-bit pre-collars, while six Eastern Metals holes used mud-rotary pre-collars. Neither technique recovers usable samples, so the upper portions of those holes produced no assay data. Kidman drilled some diamond holes from surface but sampled oxide intervals only sparingly.

Managing Director Glen Diemar described the programme as a relatively low-cost way to test the previously overlooked oxide zone. He said a review of the historic drilling showed "many intervals had never been sampled".

A longer gold corridor

Combined with AGC's own recent drilling, the historical results indicate gold mineralisation along a corridor of approximately 1.9km, running from Kelpie Hill through Evergreen to beyond Windmill Dam.

That is an interpretation of scattered drill data rather than a defined resource. The intercepts reported so far are modest in width and grade, and their continuity between holes has not been demonstrated. Oxide gold can be attractive because weathered material is often easier and cheaper to mine and process, but no metallurgical testwork or economic study on the Browns Reef oxide material was cited.

Project and company background

Browns Reef, covered by exploration licence EL6321, forms part of AGC's South Cobar Project in New South Wales. The company is seeking approval for 3,000m of RC drilling at Evergreen.

Separately, AGC is known for its Achilles discovery, where an initial mineral resource estimate of 38.5 million ounces of silver equivalent has been reported, with 58% classified as indicated. The company reported $7 million in cash and no debt as at 31 July. That cash position will need to fund several concurrent programmes, and future exploration may require additional capital.

Why it matters

Re-examining existing core is far cheaper than drilling new holes, and it can quickly highlight areas that deserve fresh drilling. For an explorer, that can make exploration budgets go further. The approach also suggests that historical datasets in the district may contain more information than earlier sampling captured.

However, historical core can have limitations, including the condition of stored material and the absence of complete records for some intervals. Results from re-sampling also need to be confirmed by modern drilling before they can contribute to any resource. The announcement did not say how many holes remain unsampled, so the scale of the remaining opportunity is not yet clear at this stage.

Next steps

Assays are pending from a 21-hole RC campaign targeting what the company calls the high-grade Hillston Structure. AGC said it intends to continue re-logging and sampling historical core across the Browns Reef area, while awaiting approval for the planned 3,000m RC programme at Evergreen.