Goldbug2 MXT F75 Relative Depth / Sensitivity Comparison

[Jim Hemmingway]

Hi Everyone…

I wondered if you guys would like to see some VLF ground depth test results over a range of target sizes. These results may differ from what you experience over your ground…

The purpose of the chart below is to present relative, side-by-side depth comparisons over freshly buried nickels and lead “nuggets”. The soil here ground balances at GB86 with a Fe3O4 bar graph readout at 0.3% equivalent magnetite using the F75's 10” elliptical concentric…on the steeper side of moderate ground mineral magnetic strength.

The 0.5 and 1.1 grain lead “nuggets” are solid and compact shaped, whereas the other test pieces are oval-shaped and reasonably flat. All units were tested in the motion all-metal mode, maximum gain (and max Goldbug2 volume), and a neutral ground balance. The Goldbug2 was run at “low mineral” setting for best signal response. The chart designations B = barely F = fair G = good E = excellent… refer to signal strength.

As freshly buried disturbed ground targets, these test targets do not signal as well as can be expected from targets that have naturally settled into undisturbed ground over many years. High residential EMI made it difficult to assess small or deep target signals when using high gain settings on the MXT. Small coils are more stable under such conditions, and produce more distinct signals.

The results are pretty much what we would expect. Small coils are relatively quiet and stable because they see less EMI and ground mineral. They see small targets better than larger coils, but don’t see as deeply on larger targets. DD coils have no apparent depth advantage in this soil, despite that they see less ground mineral. Slight differences between various targets and coils are indicated with “+” signs in the chart.

The chart results do not account for the “distinctness” of a signal. Despite generally lesser signal strength over these targets, the GB2 produces a more distinct or discrete signal over the 0.5 and 1.1 grain targets than did the stronger but less discrete F75 signal. The GB2 hits on these targets even with the sensitivity significantly reduced, whereas the F75 is highly gain dependent on the very small stuff.

The MXT result over the 0.5 grain piece using the 6” shooter coil is “soft” because some days no signal could be had at all. MXT was ground balanced and GB locked prior to testing.

Jim.

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[Jim in Idaho]

Thanks, Jim. Always enjoy your posts. They give good info you often can't find anywhere else.
Jim

 

[Jim Hemmingway]

Thanks Jim… all repetitive testing was done wearing Nugget Buster headphones set to a volume three clicks below maximum. But it still isn’t easy to gauge and compare side-by-side detector responses to these targets, and especially so since my hearing isn’t what it was years ago.

On the face of it, the chart is misleading on the Goldbug2 ratings, especially over small stuff.
For example, even with the Goldbug2 volume control set to maximum, the unit gives a lesser volume response than either MXT or F75, or at least it seems that way to me. Yet its signals over tiny stuff are definitely more distinct overall… so despite the lower volume, they’re better signals IMO. The F75's signal is more "ratty” but a stronger response… I’m not sure whether that results from signal strength or higher volume. Over all other targets, the F75 is a solid improvement with respect to overall signal response from either the 10” or 6” elliptical concentrics.

Jim.

 

[Steve Herschbach]

Thanks Jim.

Pretty much as I would expect though I was surprised to see the F75 with 10" concentric pretty much outperform the GB2 with 10" concentric across the board.

I did a similar test many years ago with more detectors in more mineralized soil. It raised a major ruckus from some hidden Minelab groupies when I revealed that the SD2200 could not detect small gold a VLF would easily hit. These days it would be commonly accepted as true but at the time it was pretty controversial. I may have to repost the report on my site when I get time. The differences were more pronounced as the soil mix was pretty heavily spiked with magnetite.

Steve Herschbach

 

[Jim in Idaho]

Thanks Jim… all repetitive testing was done wearing Nugget Buster headphones set to a volume three clicks below maximum. But it still isn’t easy to gauge and compare side-by-side detector responses to these targets, and especially so since my hearing isn’t what it was years ago.

On the face of it, the chart is misleading on the Goldbug2 ratings, especially over small stuff.
For example, even with the Goldbug2 volume control set to maximum, the unit gives a lesser volume response than either MXT or F75, or at least it seems that way to me. Yet its signals over tiny stuff are definitely more distinct overall… so despite the lower volume, they’re better signals IMO. The F75's signal is more "ratty” but a stronger response… I’m not sure whether that results from signal strength or higher volume. Over all other targets, the F75 is a solid improvement with respect to overall signal response from either the 10” or 6” elliptical concentrics.

Jim.

Jim, I don't want to hijack your thread, but I have a question. I've been working on locating an old mine. I eventually found the adit, and it goes in about 60'. I assume they got all the silver. But, I think there may be more of this silver along the fault zone, which extends for about 1/2 mile. The original discovery was made in the late 1800's, but it was lost for 60 years, and finally located again, and mined in 1950. I've been over the area with my GMT with no results, and here's my question. If looking for a rich silver vein (the ore was supposed to assay at $2000/ton in 1950) would I be better off with a TM808, or a TDI? I doubt they did any significant prospecting in 1950...the extent of what they mined just wouldn't have been worth a lot of non-paying excavating, and there's no evidence of other work along the fault zone. The ore they mined was visible at the surface.
Any help greatly appreciated.
Jim

 

[Jim Hemmingway]

Hi Steve… saw your post and decided to stay up for awhile… you are about four hours earlier than here. I had hoped this thread would generate some discussion. Others must have done similar tests over their ground, and I’ve got my fingers crossed that a few of them will post their results.

The subject of discrete signals vs loud signals should have been addressed more thoroughly in the introduction. As I mentioned to Jim above, signal volume definitely plays a role when comparing signals between these units. The F75 generates a louder, easier-to-hear signal over most of these targets.

There’s no doubt the Goldbug2 gives a more distinct or intact signal on the tiny stuff, whereas the F75 produces a less discrete “ratty” but louder signal. It isn’t so easy to objectively assign a comparative rating. My criteria is which unit produces a signal that I prefer, and by how much.

The F75 clearly produces equally discrete and stronger signals when signals are compared over most of the other targets using either the 10” or 6” elliptical concentrics. This is especially evident as we see the Goldbug2 losing signal strength over the 7” pennyweight and the 10” nickel by comparison.

Despite that we all enjoy these comparisons… I try to keep in mind that one of our most successful silver hunters… an individual retired from teaching at a local school of mining engineering… uses a Goldbug2 exclusively for silver hunting. Not the best unit for the application, but it is difficult to argue with outstanding results...

Jim.

 

[Jim Hemmingway]

Jim... was this detectable native silver that was mined? If so it would depend on how close the silver is to the surface. I cannot answer your question more directly because I have no firsthand knowledge of the TM808... never used one... anything I might say would be talking through my hat. As to the TDI... it depends on size and structure of native silver as to how well it will respond... especially if the ore lies at depth. But if I wanted max depth, my first choice would be a Minelab PI.

Lets open this question up to others with firsthand experience at tracing veins. We've got lots of miners on this forum. Steve may be able to help with what equipment would be best suited to this task, maybe he will comment on the TM808.

Jim.

 

[Hoser John]

Fun fact is some folks can/will/do much better with these units than your test. One man's pain is yet anothers esctasy and dedication throughout the years has taught quite a few "tricks" to make certain units just sing. Notice I did NOT name any units so no sniping but.......a tesoro lobo supertraq with the tiny 6" coil,all metal,set up right is deadly too on tiny TINY nuggets-John

 

[Steve Herschbach]

There is no straight answer TDI vs TM808. The TM808 needs very large masses. If the vein has lots of relatively solid coffee can size and larger masses of silver it might be an option. In general I would vote Minelab PI but after seeing some of Jim's chunks of silver a TM808 is a possibility. One very serious advantage to the 808 is it ignores stuff much smaller than a fist size target so can be good in trashy locations.

Steve Herschbach

 

[Jim in Idaho]

There is no straight answer TDI vs TM808. The TM808 needs very large masses. If the vein has lots of relatively solid coffee can size and larger masses of silver it might be an option. In general I would vote Minelab PI but after seeing some of Jim's chunks of silver a TM808 is a possibility. One very serious advantage to the 808 is it ignores stuff much smaller than a fist size target so can be good in trashy locations.

Steve Herschbach

Jim, Steve,...thanks. From the story, the silver was very rich, but after finding the drift, was limited in quantity...just the single deposit. I have some faint hope there is more along the fault, at enough depth it couldn't be found with the methods available at the time. I think I'll probably try the TM808, simply because it's the lower-cost alternative. If it doesn't show anything, then I'll consider getting in a little deeper. About 5 miles across the range there is a mine that at one time was Idaho's second largest silver producer, so there was some decent silver in the area.
Jim

 

[Jim Hemmingway]

Hello John… there’s no question about your depth comment. These tests were done repetitively over cool wet springs, summer heat and drought conditions. Responses do tend to vary according to weather changes but also because I’m in very high EMI residential area. And these are disturbed ground targets… depth / sens is definitely reduced compared to naturally occurring targets in the field.

So I’ve tried to emphasize the above results are relative only, and assigning ratings is somewhat subjective. I’m certain that 10 different guys doing the same tests here would have slightly different impressions. But these results reflect my evaluation. There’s nothing mysterious about them… anyone possessing these units / coils can do the same tests over their ground and report them here. By all means do so.

BTW, I had a chance to quickly run a Gold Bug Pro over my test plot. Not a long-term side-by-side comparison with other units, but I put it into the all-metal motion mode one night, and ran up the sensitivity using the 5” round coil. It matched the units in the chart for response to the small stuff… maybe even a bit better… and that coil responded to the 10” nickel with what I’d characterize as a “fair” signal.

Jim.

 

[Jim Hemmingway]

Jim… good luck with your project… it sounds like the sort of thing I would enjoy doing with you were it convenient to do so. Possibly those two minesites have a connection.

I would not abandon using the TDI with a larger coil just yet... if you happen to already own one. Equipped with the stock 12” DF coil it matches or exceeds my Infinium equipped with the 14” mono. And the Infinium easily found the piece below at “shoulder-in-the-hole” depth… not massive silver... but rather a highly crystalline native silver specimen. It produced a fairly quiet but unmistakable hi-lo zero discrimination signal… a signal that altogether disappeared in reverse discrimination.

All the best with everything...

Jim.

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[Jim in Idaho]

Jim… good luck with your project… it sounds like the sort of thing I would enjoy doing with you were it convenient to do so. Possibly those two minesites have a connection.

I would not abandon using the TDI with a larger coil just yet... if you happen to already own one. Equipped with the stock 12” DF coil it matches or exceeds my Infinium equipped with the 14” mono. And the Infinium easily found the piece below at “shoulder-in-the-hole” depth… not massive silver... but rather a highly crystalline native silver specimen. It produced a fairly quiet but unmistakable hi-lo zero discrimination signal… a signal that altogether disappeared in reverse discrimination.

All the best with everything...

Jim.

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Thanks, Jim...that's a gorgeous piece for sure...I wonder if the TM808 would have "seen" that?
Jim

 

[Jim Hemmingway]

Thanks, Jim...that's a gorgeous piece for sure...I wonder if the TM808 would have "seen" that?
Jim

Jim… based on the information and videos over on the White’s website, I think it would signal over that piece. According to White’s the TM808 will see a metal object sized at 3” square in the neighborhood of 3 ½ feet deep… presumably that figure is for average ground mineral magnetic susceptibility. And adjusting the unit to soil minerals looks simple enough. It might be a bit awkward to use on a hillslope.

Could be that your research indicates the (presumably) native silver in the area had indicative associations… for example black sulfosalt (stephanite, polybasite, etc), the ruby silvers (proustite and pyrargyrite), silver sulfide (acanthite)… or possibly other materials sometimes associated with silver. In this area we see a lot of cobalt, niccolite, safflorite or skutterudite and many others. It would certainly pay to look for any unusual dark material, and of course any oxidized staining or discoloration… in particular (annabergite) green nickel and (erythrite) pink or red cobalt “blooms” as per the photos below. These are a common sight in our silverfields…

Jim.

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[Jim in Idaho]

Jim...many thanks...I saved the pics. It's really nice to know what to look for. I think I'm going to get a TM808 to start with. I have no idea what form the silver took originally. It was found, in late 1880's by an old guy who went by Texas Jack. According to legend, he was found, ill, and the guys who found him hauled him to the hospital in salmon City (now Salmon, Idaho). He was dying of pneumonia, but wanted his saviors to know where the ledge was located, so gave them directions. I had to do a lot of research to find one of his landmarks, but eventually did. That led to finding the adit. The rest of the story was that they were unable to find it. Forward in time to the early 1950's, and two guys bear-hunting found float from the ledge, but didn't know until later what it was. The story said they were also unable to locate it. That was apparently untrue, as it was claimed in 1950. The claim was allowed to lapse in 1951, so it was only worked for one summer. That would agree with the evidence left at the location..not enough junk left for an extended operation. I found a couple of carbide lamps, and some old boots, axe head, shovels, etc. The drift is about 60' deep, and about half the holes in the face are drilled....that means they probably had a breakdown, and just decided to bag it, rather than do the repairs and start in again. I was a little surprised they didn't shoot the holes they had drilled. The drift is very clean, and about 8' diam. It is located right at the fault line between the rock types. The face is fairly porous, with gaps in the fault zone, and some pockets of crystallization.
I'll keep you posted. It will be awhile before I can get in there, of course...it's till winter here...LOL If you get down this way, I hope you'll look me up.
Jim

 

[Jim Hemmingway]

Jim… looking over these posts… it seems to me that the first step is to establish whether the silver ore contained detectable native silver… before buying additional detecting equipment. Searching with your GMT ought to have produced a few small silver samples. Silver sulfides / sulfosalts without native silver present are not suitable candidates for metal detecting.

I’ve included photos of two more typical field examples of silver minerals that may be helpful to you. There is quite a selection of mineral photos and information available at this site…

Gem and Mineral Collector's Information and Photo Gallery, crystals

The first shot is dark ruby silver combined with native silver in calcite. Ruby silver comes in two basic forms, proustite… usually lighter in color… and pyrargyrite. The ruby silver in the photo below is a fresh surface. A weathered surface usually forms a dull light silvery or gray coating / patina. I’ve also seen plenty that is very dark red … but either produces a deep red streak. In the field, rub just about any handy small rock against a suspect ruby surface = dark red powder.

The next shot is an acanthite / native silver specimen. Acanthite is a silver sulfide comprising 87% silver and is often associated with wire silver here. It is black, quite soft and sectile… but sometimes with a slight bluish-black tint in this area.

That’s it Jim…again… good luck with everything. The exploration sounds intriguing… we can’t succeed unless we get into the field and make an effort. Please think personal safety first.

Jim.

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[Jim in Idaho]

Jim, I think the ore probably did contain visible silver. I know many of Idaho's silver mines did. And, I suspect that visibility is what led to the initial discovery. I don't know that, but suspect it's true. I did a little checking with the GMT, but got busy with work, and never got back there to do a good survey. That will definitely be the first step this spring. The tailing pile is on a steep hillside, so should be easy to shovel down and examine things. I appreciate the pics....knowing what to look for is half the battle.
Jim

 

[Gold Itch]

Jim, I hope you don't mind me waking up this thread but it deserves to be given an Airing once in a while,

Anyways I have been testing out all the Whites Coils that I have for the MXT A/P and one thing that I have noticed is that the 4x6 and the 6x10 are no more sensitive to small items than the 10" DD (D2) Coil and during my testing I had the Gain running at Max in the Prospecting Mode.

This past month or so I bought the 6x10 (5x9) Eclipse DD and the 4x6 DD Shooter and the 5.3 (6 inch) Eclipse round Concentric and today (10/8/16) I got the X pattern 950 Eclipse Concentric, When I compared the 6x10 to the standard 10"DD in and air test on a US Quarter it looses about 2 to 2.5 inches to the 10" DD, and on bits of lead weighing 0.02 grams they were both equal Except the 5.3, The 4x6 shooter looses about 4 to 5 inches in the Air to the 10" DD on Coins but see's the 0.02gram bit at the same distance, Now I have never understood what all the fuss was about with that 4x6 because a heck of a lot of people use them, but I have always thought of it as a Dog of a thing,

Anyways, had to order another set of Scales because I need some that had a 5 1/2 digit read out because although I already have 3 sets and one set being worth about $1400.00 they still did not go down low enough, Having read GSA's story about the MXT and the 5.3 coil I thought I would give it a another try because I have always had a 5.3 up until about 4 years ago. And I have to admit is what GSA say about that setup is 100% correct and then some.

So now it was time to start testing the 5.3 (6") concentric, This is where things really made a difference, Once fitted to the MXT A/P I cranked up the gain (As Before) and now the MXT is seeing bits well into GMT, GB II and GR Territory on Very Tiny bits and on a US Quarter it see's them at the same distance as the 10" DD depending what mode I use, So after some head scratching I thought I would take the whole setup out side and see what faint targets I could find,

The builders replaced the Lead on the roof and from around the windows here about 2 years ago, So you can imagine what I found, Anyways I got this soft target come through the head phones after about 30 minutes and when I worked out exactly where it was it then took me another 20 minutes on my hands and knees to find It with a 10x power magnifying glass, So once I had it safe it was back indoors to clean it and weight it, It turns out to be the Tiniest piece of metal/Lead I have ever found with a VLF as in the VLF range Not LF machine,

As some of you know I made my GMT as hot as the GB II if not more so just by adding the GM II coil to it and That also lowered the GB setting too, So that was another bonus, and it is a lot hotter than the 4x6 shooter when fitted on the GMT and it see's Extremely tiny targets at 3 X the distance that the Factory Twin "D" coil does. As in bits that can't be weighed the size of a piece of Glitter,

Anyway back to the MXT A/P and the 5.3 Coil, That bit I found was about 3/4" Deep in the ground, so I got out the new scales and calibrated them to make sure they were spot On

AND.... It weighed 0.00019 ozt, or 0.0925 grains, or 0.006 grams.

Now in my books that is pretty good going for a VLF regardless of the brand, And in the Air that coil can see a bits weighing 0.10 grams at about 2 to 3 inches depending on the EMI.

If you happen to own an MXT then the 5.3 coil has many other uses and it can hit coins in to the 7 to 10" inch range In the Ground and it is a real Gem in junk filled ground, truly I think that the 5.3 Coil Seriously shows an advantage over the 4x6 in comparison,

In the Air on targets weighing around 0.02 grams all the DDs will see them at around 1" . Where as all the Concentrics see them at 2 to 3 inches with the 5.3 giving the strongest signal of all going up to 3 to 4 inches, But on smaller targets the 5.3 will see them at about an inch 1 to 1.5 inches and the DDs will see them when they are about 1/4" from the Coil, I also have one target that the GMT can see and the 5.3 can see it between 1/4 to 3/8 an inch the Only problem is it is too small to be Weighed,

In your chart you used the 5" coil on the F75 with good results, So I am thinking that the 5.3 coil would give the MXT a bit of an advantage because it is extremely sensitive and it is the most sensitive Coil out of any of the Whites Coils, and although it is a Concentric because of it's small footprint it does not suffer from hot ground conditions and allows you to run the Gain up higher and as you know in hot ground conditions lower KHz machines suffer less,

One last note, Is that on all small targets the 5.3 saw them a 3 X the distance compared to the 4X6 Coil,

Thanks again Jim take care.

John.

 

[Jim Hemmingway]

Hi John… hope you are doing well… we’re busy packing to head north for our annual extended prospecting trip. Saw your post here tonight and figured I’d better reply now before getting busy with something else. There is a lot of preparation for a lengthy trip, and double-checking lists of food, clothing, equipment, charging batteries and so forth… to finally be ready to leave. Meanwhile the wife was out shopping today… my list calls for 20 cans of pork and beans, tasty munchies for rainy days, tea, and all the usual staples for outdoor cooking and fine dining by the fire.

Sooooo… it certainly looks like you’ve been busy testing with your MXT and accessory coils… lots of fun. Air tests have some use, particularly when evaluating rock samples for both conductive material and for non-conductive ferromagnetics… but otherwise we prefer to do all other testing on naturally settled targets. Since that is so darn inconvenient most times, next best thing is to establish a longterm test plot in the backyard for relative depth comparisons over those particular soil conditions. In other soils, especially over naturally settled targets, those relative results may change and the depths acquired may improve. Magnetic susceptible iron minerals do make a difference, as does the type of substrate and moisture content. Test plots really have little value for anything else, other than to demonstrate what happens when you detect over disturbed ground, mimicking for example urban renewal projects where a lot of soil is displaced or moved around. Non-ferrous target ID and therefore discrimination are not terribly dependable beyond a few inches depth here, although small iron normally does target ID within the iron range.

I agree that the small MXT shooter coil didn’t impress me after becoming accustomed to how well my F75 and similar shooter coil performed, but it ought to have some benefit in trashy areas. Frankly I never use that combination as I much prefer the F75 with the small 6” elliptical concentric. I’m not surprised you’re impressed with the 5.3 coil results, it looks to be quite a versatile coil over a wide range of type and size targets. The concentrics are better discriminators, especially with target ID on shallow small iron such as nails. We rarely ever use discrimination for rockhunting, but prefer to stick with motion all-metal mode, dig weaker signals, and use target ID in combination with auto GB to evaluate suspect stronger signals. Mind you, nothing to date is infallible and we do dig lots of junk, particularly large iron such as drill rods, iron bars, or larger drillbits at depth when using VLF units.

The 6”X 10” Eclipse DD isn’t terribly deepseeking but it is relatively lightweight, is good in trash, and is plenty sensitive enough for me in the motion all-metal prospecting mode where our desirable native silver signals weigh ounces and more. Incidentally, the chart initially presented to start this thread was more for the goldhunters or anyone with an interest in those particular detector brands.

Your remark “just by adding the GM II coil to it and That also lowered the GB setting too” seems a bit odd. A concentric sees more dirt than a same size and shape DD and that should translate into a less conductive (higher number on the ground balance scale) GB readout. For example on my F75 the GB readout with the stock 11” elliptical DD is GB83 here, whereas the elliptical 10” concentric readout is GB86 over the exact same place on the lawn. I’d have to double-check but I think the F75 5” round DD produces a GB79 readout and at the moment I cannot remember where the 6” elliptical concentric reads.

It seems that you’ve spent considerable money on weight scales. I have two weight scales for measuring small stuff. One has an eight-ozt capacity and an accuracy of 0.1 grams. The other scale is named HP-100X with a capacity of 100 grams and an accuracy of 0.01 grams or if you prefer… that is 0.1543 grains. That would be more than sufficient for me, regardless whether we hunted silver or gold. Both these scales cost somewhere around $50 plus or minus a bit. I know they were inexpensive but I can’t recollect the actual prices at the moment.

That’s about it for now, I always enjoy discussing metal detection with you, although I am rather tunnel-visioned since we pretty much restrict our detecting to naturally occurring silver over here. All the very best with everything this autumn John, hope you do wonderfully well with your MXT, and hopefully we’ll get back in touch before Christmas and compare notes again.

Jim.

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[nuggetshooter323]

Jim,
Were the MXT results that you got still be valid for the updated MXT All Pro? I'm going to buy another VLF, and I've been eyeing the the updated MXT. But with those results I might have to go with the F75.