A big gold nugget can give a faint signal when the coil is still well above it, when much of the nugget is quartz rather than solid gold, or when its broad, soft response blends into the ground noise. In mineralized ground that soft signal is easy to write off as a hot rock or a change in the soil. The 1.2 kg (2.7 lb) "Tibooburra Spud" dug in outback Australia in October 2026 is a recent case: its finder says the signal was weak for the size of the piece, though the gold showed at about 4 inches, and the report does not say why.
The Tibooburra Spud find
As reported by ABC News in Australia, a Broken Hill prospector who asked not to be named found the nugget on Mount Stuart station near Tibooburra, in the far northwest corner of New South Wales, near the end of a day's detecting in mid-October 2026. The nugget weighs 1,218 g (about 2.7 lb) and is flecked with quartz. Testing put its gold content at roughly 940 g, a little over 30 troy ounces, worth around A$150,000 to A$160,000 on gold content alone, with more possible if it sells to a collector.
He was running a Minelab GPZ 8000. By his account, the target did not sound like a big piece. Once he was down about 100 mm (roughly 4 inches), the detector was squealing, and on the first or second scrape he saw a bright yellow dot in the center of the hole. The report does not say why the signal was soft, so the sections below cover the usual reasons a large nugget sounds smaller than it is.
Why does a deeper target give a weaker signal?
A detector coil sends a magnetic field into the ground and listens for the field a target sends back. Both legs of that trip weaken with distance, so the response falls off much faster than the distance increases. Taking dirt off the top of any target shortens that distance, which is one reason a faint signal can turn loud partway down the hole.
Our guide on how deep metal detectors go covers real-world depth figures. The point here is the shape of the curve: near the edge of what a detector can hear, a couple of inches makes the difference between a clear target and something you can barely pick out.
Gold in quartz responds differently
A detector responds to the metal, not the rock around it. Gold spread through quartz, in seams or patches, can respond more weakly than a solid nugget of the same gold weight, because the gold is not one continuous piece of metal. Gold is also very heavy, so a specimen can be mostly quartz by volume while still being mostly gold by weight, and look bigger in the hand than its signal suggests. The Tibooburra Spud is about 77% gold by weight and visibly flecked with quartz; the report does not say whether the quartz played any part in its soft signal.
What a large, soft signal sounds like
Small, shallow gold gives a quick, sharp response. A large target that is deep, or that the coil only partly couples with, gives a slow, wide one: the threshold swells as the coil approaches, peaks over a broad area and fades away again. In mineralized ground, that is very close to what the ground itself does when you cross a patch of hotter soil, a clay seam or a low spot.
In my experience, a large, deep target often doesn't give a loud, obvious response at all. It's a faint, drawn-out swell that is easy to miss at normal swing speed. What matters is whether it repeats. If it keeps coming back after I've rechecked the ground balance and the coil position, I dig it rather than writing it off as ground noise. A big piece of gold near the limit of what the detector can reach can sound surprisingly subtle, although hot rocks and buried iron can sound much the same, so not every repeatable soft signal is gold.
Three checks help separate a real target from the ground:
- Sweep from another direction. Ground variation usually changes shape or disappears when you turn 90 degrees. A real target keeps coming back from the same spot.
- Scrape and recheck. Remove an inch or two of soil with your pick and swing again. A real target gets louder as the overburden comes off. Ground noise usually does not, though the hole itself can change the ground signal, so check the spoil pile too.
- Lift the coil. Raise the coil a few inches over the spot. A small, shallow target drops out almost at once; a large, deeper target fades more slowly.
Where the answer changes
Mineralized ground
Ironstone-rich soils like many of the Australian and Western US goldfields produce more ground noise, and ground noise is what buries a faint signal. The GPZ 8000 offers four ground types for different conditions. Picking the one that keeps the threshold smooth matters more than running maximum sensitivity: a noisy threshold turns every faint target into a guess.
Coil size
Larger coils reach deeper on bigger gold and cover more ground per swing. Minelab designed the GPZ 8000's standard Z18 18-inch coil for depth and stability in highly mineralized ground on medium to large gold, with the optional Z13 13-inch coil aimed at small to medium gold in brushy ground. A small coil is more sensitive to small gold but loses large, deep gold sooner.
Detector type
For large gold at depth in difficult ground, prospectors reach for high-end pulse induction and ZVT gold detectors like the GPZ 8000 and the Minelab GPX 6000, which Minelab rates for gold of all sizes. The Minelab Gold Monster 2000, a hybrid of VLF sensitivity and a pulse induction soil-handling engine that Minelab calls Multi-Au, comes with a 5-inch coil and is built for ultra-fine and small gold instead. On a patch with big gold in it, that is the wrong tool for reaching the deep pieces, and the right one for the small gold that the big coils skip over.
Common mistakes with faint signals
- Skipping targets that don't sound like gold. The Tibooburra finder's advice to other prospectors was simple: "keep swinging [and] keep digging every target." On old ground, the easy signals are long gone. The faint ones are what is left.
- Stopping at a shallow scrape. If the signal is still there after the first few inches, it is deeper, not gone. Recheck the hole and the spoil pile before you move on.
- Swinging too fast or too high. A faint, wide signal needs a slow, low, overlapping sweep to build up in your ears. Lifting the coil at the end of each swing costs depth exactly where you need it.
- Running too hot for the ground. More sensitivity only helps while the threshold stays smooth. Past that point, ground noise hides the very signals you are trying to hear.
Next step
If you prospect in mineralized ground and want to reach deep, larger gold, start with our guide to the best metal detectors for gold, then compare models in our gold detectors collection. Questions about which detector suits your ground? Call or email us; we are happy to talk it through.
Detectors in this article
| Best for | Detector | Price today |
|---|---|---|
| Also covered | Minelab GPZ 8000 | $9,999.00 |
| Also covered | Minelab GPX 6000 | $6,999.00 |
| Also covered | Minelab Gold Monster 2000 | $2,399.00 |
Prices are live from our store and update automatically.
