Garrett Infinium question.

[Jeff in ME]

A question for Steve, or anyone else who may know.

What would be the minimum size in gold that the Infinium LS would be able to detect with the 10x14 mono coil? Would using a smaller coil, such as the 8 inch mono coil, give me any improvements or allow me to detect anything smaller, or only give me a reduced depth with the same size of gold detected?

[Steve Herschbach]

Hi Jeff,

Mono coils on a PI are kind of weird on small stuff. Either the 14" mono or 8" mono can hit a 3-4 grain (480 grains per ounce) nugget if it nearly touches the edge of the coil. So you get two hits as the coil passes, one on each edge.

To get a signal in the center of the coil takes a bit larger item with the 8" mono, and a bit larger yet with the 14" mono. Wish I could be more specific but it would depend of the purity of the gold, and shape, like round or flat.

The cutoff for small gold with a PI is governed more by the pulse delay than the coil size. So you don't get as much of a boost going to a smaller coil as you would on a VLF detector.

[Steve Herschbach]

Hi Jeff,

Have you run a detector there or know someone that has? Is there an issue with hot rocks or extremely mineralized ground? If not, I'd stick with a VLF unit. A PI has no real advantage in a situation like you are describing unless you have an issue with ground mineralization. We have small gold, low mineral conditions south of Anchorage and almost nobody uses PI detectors for that reason.

[Jeff in ME]

Hi Steve,

Yes, I guess the PI unit would be pretty useless to me there. I'll stick with the VLF. Thanks for the info.

Jeff

[Jim Hemmingway]

Hi Jeff,

I own an Infinium and used it with good success silver hunting this past autumn. I will be posting an article on our forum within a week or less about my experiences with the Infinium. It details every facet of using this unit for detecting nuggets and ores.

To supply an answer to your questions, I’ve pasted together a lengthy reply that is designed to take you along a learning curve I’ve experienced, so that you will have a better perspective when evaluating my findings. Steve has nailed it down, but here’s a bit more to contemplate from a newbie's vantage point…

First, it’s not easy to get solid information as to what depth/sensitivity on any given size/weight nugget can be expected from Infinium or any other unit. This is because of variable factors that affect detection depths. These include soil conditions, target purity, size, shape, structure, nugget profiles presented to the coil, test area EMI conditions, and even user skill level. For example, its not uncommon to think you’ve recovered a small piece deeper than where it actually gave a signal and then became dislodged while digging. I suspect such errors do make their way into reports we read about.

Air tests don’t represent soil depths. Some reports indicate that PI units can do better in the ground than in the air. I saw clear supporting evidence when testing Canada nickels, but I have not tested the same nugget both in the air and in the ground for a further comparison, and can’t until spring comes. This air vs ground depth phenomenon is well explained over on the TDI forum by well-known member “Reg”. I mention this phenomenon here, because I’ll refer to some air tests below.

So, with the above in mind, what might generally be expected from Infinium on depth over small nuggets as far as I’ve been able to determine?

I’ve read a report from a (formerly) respected source where nuggets air tested right down to around a few grains at respectable distances with the 14” mono. One nugget at 0.22 grams (roughly 3.4 grains) that tested exceptionally well out to 12 cm, was described as a solid flat piece. By stark contrast, I noticed that a 0.33 gram (roughly 5.1 grains) nugget with “character” did not air test nearly as well, only out to 3 cm. Another small, solid and flat piece at 0.15 grams (roughly 2.3 grains) air tested out to 7 cm.

The air test distances on one-half gram to one gram nuggets in this report tally closely with my air tests on same size, solid nuggets as mentioned in my report and below. My results on similar size and shape, solid smaller nuggets do not support the target response claims above at all.

In the above report, there generally was a correlation of nugget size to distance detected, but there were a number of exceptions that likely can be attributed to differences in shape, and structure (character). So, differences in size, shape and structure = detection depth variability.

There are several examples of PI users finding small nuggets varying in size from several grains to a gram or so. Some of them mention decreased depth results in the air or even that such finds cannot be detected in the air. There are such reports on the first few pages of the Infinium forum, if you are interested.

Now, with the above said, I have a solid, flat two-and-one-half grain gold nugget that will not respond to any of my coils in an air test (have all the coils except the 3”X 7” DD). That same nugget happens to be presently buried at three inches in the patio, and also will not respond to any coil on Infinium.

A solid, fairly flat 0.3 gram (5 grain) lead “nugget” will not air test respond to the 14” mono coil here unless rubbed right on the coil. It will respond out to about an inch on both the 8” mono and 10” elliptical DD coils (maybe it’ll do better in the ground, right now I don’t know). However, if you bump up that size to a half-gram, both the 14” and 8” mono coils will give a good signal at 5 inches in the air. But neither coil will signal on a different (but fairly solid) half-gram nugget in the ground here at 4 inches.

Testing a compact, solid one gram silver nugget, Infinium will air test with a full signal at 7.5 inches with the 14” mono coil, 5inches with the 14” DD coil, 6 inches with the 8” mono coil, and 4+ inches with the elliptical 10” DD coil. While in the field I reburied this nugget at 4” and got an excellent signal with the 14” mono coil.

Here at home, the 14” mono will not respond to a fairly solid one-gram nugget freshly buried at 5 inches in the test plot. It will signal on a fairly solid pennyweight nugget freshly buried at 5 inches, but not every sweep. My other coils fare no better on either nugget. However, these are high EMI tests and the nuggets are in disturbed ground. Both of these factors will diminish depth, if anything.

However, my VLF units, the F-75 and Goldbug2 will easily see all of these targets with stock coils over this high mineral ground, supplying signals you can’t miss. With smaller coils these VLF signals improve even more on shallow targets. Even the MXT signals over some of these targets using the stock coil. However, the Infinium with the 14” mono will slightly exceed my F-75 in JE mode (with or without a small iron discrimination setting of “12”) (stock coil) on a larger target such as 10” deep nickels. It’s very close, and it does have the advantage of the larger 14” mono coil. Of course, if magnetic ground minerals were to increase more, one would expect VLF depth/sens performance to correspondingly decline to where Infinium would be more effective.

I have quite a number of silver nuggets in the foil/nickel conductive range with weights in the half-gram to gram range that respond poorly compared to more solid compact nuggets of similar weight/size. Some do not respond at all, but give a strong signal with the VLFs. When I read about PI users posting nugget finds between a few grains and say roughly a gram, I wonder if they passed over other nuggets and did not know it. I think that’s a reasonable concern.

So as you can see, I have some concerns about using this unit at least for small gold down below a gram and especially below a half-gram. My limited test results on small nuggets do not support depths I see reported elsewhere. I trust what I see with my own eyes.

Jim.

[Jeff in ME]

Thanks, Jim.

The reason I asked the question originally was because I wanted to know what the smallest size gold that could be found and at what depth because I had considered using the Infinium under water where the largest gold I've found yet was no more than 10 grains. I guess I need to find a way to waterproof one of my VLF detectors.. I'm trying to find an alternative to dragging a subsurface or surface dredge 6.2 miles through the woods.

[Steve Herschbach]

Hi Jeff,

If the ground is not very hot, you might research the Tesoro Tiger Shark. It is the most sensitive underwater VLF unit at 12.5 kHz and one of the few like the Infinium that offers interchangeable coils. It does have the all critical ground balance control. I've been meaning to get one myself as I've cornered a supply of 4" coils for it, but the darn detector has been unavailable since last summer due to lack of some part. If looking for a used one it has an immediate predecessor called the Stingray that is also a very good unit.

[Jeff in ME]

Hi Jeff,

If the ground is not very hot, you might research the Tesoro Tiger Shark. It is the most sensitive underwater VLF unit at 12.5 kHz and one of the few like the Infinium that offers interchangeable coils. It does have the all critical ground balance control. I've been meaning to get one myself as I've cornered a supply of 4" coils for it, but the darn detector has been unavailable since last summer due to lack of some part. If looking for a used one it has an immediate predecessor called the Stingray that is also a very good unit.

Hi Steve,

I looked at the Tiger Shark yesterday. The dealer I have bought detectors from locally sells Tesoro but doesn't have these in stock either, and doesn't know when they will. I'll stick with what I have for the time being, I've looked at a couple other models and brands but they don't have interchangeable coils. Thanks for the help.

Jeff