EL9941 Coopers-Curraba — A copper mine that assayed 8.06 g/t gold in 1987, and nobody went back

The short version

Coopers-Curraba was worked, sampled and drilled three times between 1883 and 1969 — for copper and for sulphur — and abandoned each time on copper economics, not geology. The 1968 operator assayed his drill core for gold and never interpreted the results. Read now, those logs show gold sitting outside the copper lode: above it, and again below it, with the deeper hole ending inside a gold-bearing arsenopyrite zone at 79.4 m.

Then, in 1987, a different explorer sampling the same ground 2.7 km to the north-north-east picked up vein quartz from an old adit dump. It returned 8.06 g/t Au, with a repeat at 10.5 g/t. He wrote it in the ledger, concluded the area held "no major gold-bearing zone," and left.

That vein has never been found. No hole has ever been drilled on this ground to test a bedrock gold target.

Four things a geologist will want to check

1. The gold and the copper are separate systems. The massive sulphide returned 2.05 % Cu and 6 g/t Ag over 0.30 m with gold not detected. The best gold in the hole — 0.85 g/t over 1.17 m — sits in quartz-banded schist above it, with 57 ppm Cu. Below the lode, a 0.04–0.25 g/t Au tail runs through arsenopyrite-bearing graphitic schist to the end of the hole. Core recovery through those intervals is logged at 97–100 %, so this is not a core-loss artefact.

2. The deepest hole stopped inside the anomaly. MC DDH1 ended at 79.4 m still in anomalous, arsenopyrite-bearing ground. Nothing has been drilled below it.

3. The geophysical target was never adequately tested — and the regulator said so at the time. The 1968 IP survey defined an anomaly 30–152 m south of the shaft, interpreted to extend beyond 122 m. The Department of Mines assessor recommended against aid for the second hole because, at about 76 m, it was too short; an adequate test needed roughly 152 m. It was never drilled.

4. Arsenic and antimony have never been assayed on the drill core. The pathfinder elements that define modern gold targeting in this belt have been measured at surface — but never on the 1968 core, including the deep gold-bearing interval that defines the target.

Figures

Figure 1 — Gold is decoupled from copper in MC DDH1. Down-hole gold plotted from the 1968 assay sheets. The copper–silver massive sulphide (red band) carries no detectable gold. Gold occupies two separate positions: a single 0.85 g/t Au sample over 1.17 m immediately above the lode, and a persistent 0.04–0.25 g/t tail through logged arsenopyrite (to 10 %) below it, running to the end of the hole at 79.4 m. Historical 1968 AAS values, no modern QA/QC; shown as an exploration vector only.

Figure 2 — The hole stopped where it got interesting. Conceptual west–east section through MC DDH1 (schematic; the 1968 grid is local and there is no down-hole survey). The hole was drilled to cut the copper lode at 51.9–54.9 m and stopped soon after. The 1968 IP corridor, which lies 30–152 m south of this section and was interpreted below 122 m, has never been drilled. Proposed holes are conceptual.

Figure 3 — Everything on one plan, including the 8.06 g/t sample.EL9941 in GDA94 / MGA Zone 56 with the historical shaft, both 1968 collars, the IP corridor, and every 1986–87 rock chip and stream sediment. Panel (b) is Harrys Knob in the licence's northern block: the 8.06 g/t Au vein float (repeat 10.5 g/t), gossan and chert samples at 0.13–0.18 g/t Au, a massive-pyrite bed of at least 1 m carrying 0.17 g/t Au and 31 g/t Ag, an old shaft and adit, and stream sediments labelled in ppb Au. The 1987 samples are placed from the original 1:25,000 plan, ±100 m; none of them appear in the NSW MinView geochemistry database.

Figure 4 — The 1987 ledger line, as written."Float on dump — Milky qtz vein material from adit in hard rock — meta sediments." Gold: 8.06 ppm, repeat 10.5 ppm (detection limit 0.01 ppm), with 5.3 ppm As. Open-file, in the public record since 1987, and never followed up.

What the primary record actually says

"Although gold is associated with the deposit, the price of copper and the transport difficulties made operations — at that time — uneconomic."— Planet Metals Ltd, 1969

"…this massive pyrite zone has no expression along strike. The only possibility then is depth…"— P. English, 1968. Depth was never drilled.

"Mt Carrington (Coopera Curripa) Copper-Zinc-Gold Mine"— Tamworth–Hastings 1:250,000 Metallogenic Map, locality 255. The State record has listed gold all along.

Regional context is not abstract, either: within the same county, the Mummel-parish workings produced gold from quartz reefs and silicified claystone with arsenopyrite, at reported values of one to over two ounces per ton.

The counter-argument

We'd rather you heard this from us than found it yourself in DiGS.

The drill-core gold values are 1968 assays with no quality control, and the best drill result is a single 0.85 g/t sample. The 1987 explorer sampled the strike properly with a modern multi-element suite and concluded there was no major bedrock gold zone. The 8.06 g/t result is float on a dump, not rock in place. The IP anomaly may be graphite rather than sulphide — graphite alone produces that response, and the 1968 operators said so themselves. On that reading, Coopers-Curraba is background gold in carbonaceous rocks with a nuggety alluvial halo, and there is no deposit.

That possibility is real and remains open. What makes it worth testing is the cost of the answer: the source vein at Harrys Knob is a field-mapping and channel-sampling problem, not a drilling problem, and a single twin-and-extend hole resolves the deep tail. Each stage can kill the project for a modest spend.

Verify it yourself before you talk to us

Everything above is open-file. The reports are free from the GSNSW DiGS portal:

• R00029598 — 1968 drilling report and the full drill logs (the gold column)

• R00013680 — drilling-aid application and the Department's assessment ("too short")

• R00029633 — Planet Metals 1969 summary report

• R00050341 — 1983–87 alluvial sampling and the Blue Circle rock-chip ledgers, including sample D789

• R00026358 — GSNSW compilation, entry 63, Coopera-Curraba

• MinView — EL9941 tenement; drillholes MIN_520271 and MIN_520272

If you hold ground or data in the Nowendoc–Cooplacurripa district, you'll know within an afternoon whether this reading is fair.

What's behind the NDA

The Coopers-Curraba Technical Synthesis is a fully sourced technical document: every interval from both 1968 holes transcribed and cross-checked against the original log sheets; the complete 1986–87 assay data with sample locations; five defined targets with success and kill criteria; a gated work programme with costs; a JORC Table 1 stub; a verification workstream listing every item still to be confirmed; and the alternative interpretations argued against our own model.

No JORC (2012) Mineral Resource, Ore Reserve or Exploration Target is declared or implied. All grades quoted are historical (1885–1987), were produced without modern quality control, and are presented as exploration vectors only; none is reported in accordance with the JORC Code. Surface samples are grab, chip or float samples and are selective by nature. Historical results have not been verified by a Competent Person for public reporting. Coopers-Curraba also appears in the record as Coopera-Curraba, Coopera Curripa, Cooplacurripa and Mt Carrington; it is unrelated to the Mt Carrington project near Drake, NSW.