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Thread: Benchtesting Rocks & Minerals with a VLF Metal Detector

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  1. #31
    us
    Jan 2012
    Oregon Coast
    White's V3i, White's MXT, and White's Eagle Spectrum Cleangold sluice & prospectors pan, EZ-Gold Pan, and custom cleanup sluice.
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    Hi Jim.
    If you would like some of that black sand I would be happy to send you some to sample and play with...
    Heck there might even be a bit of beach gold in it.....

    Here is another pic of a black sand layer that ya have to dig a little to get to.
    This pic and the surface pics are from Cape Disappointment. It is the S.W. point of Washington State just south of the light house.

    Click image for larger version. 

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    Last edited by johnedoe; Aug 23, 2018 at 12:18 AM.
    We hold these truths to be self-evident: that all men are created equal; that they are endowed by their Creator with certain unalienable rights; that among these are life, liberty, and the pursuit of happiness. Thomas Jefferson

    Which is also why we have the second
    amendment.

  2. #32
    Charter Member
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    VERY NICE post, my friend. Informative and you do know the subject material! I have used my Gold Bug 2 for air tests many years now. I CAN use my hand to GB small samples using the GB2. The trick is (and many are not aware of this) that you can balance out the hand minerals as you would a sample. I cannot vouch for other detectors but after balancing my "hand salts" out, the GB2 will sound off on the smallest target in the hand. Good to hear from you again! ╦╦Ç
    Now remember, when things look bad and it looks like you’re not gonna make it, then you gotta get mean. I mean plumb, mad-dog mean. ‘Cause if you lose your head and you give up then you neither live nor win. That’s just the way it is. – Josey Wales

  3. #33
    ca
    Honorary Member of the Central Alabama Artifact Society (C.A.A.S)

    Jan 2008
    Canada
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    Quote Originally Posted by johnedoe View Post
    Hi Jim.
    If you would like some of that black sand I would be happy to send you some to sample and play with...
    Heck there might even be a bit of beach gold in it.....

    Here is another pic of a black sand layer that ya have to dig a little to get to.
    This pic and the surface pics are from Cape Disappointment. It is the S.W. point of Washington State just south of the light house.

    Click image for larger version. 

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    Hi William… thanks for the offer but we have lots of black sand in these parts, although not nearly in the quantity that you depict in your photos. The photo above is an outstanding illustration of layered deposits.

    Question: why is it named Cape Disappointment? Is it because there is no natural shelter / harbor available for ships caught in stormy weather? It does sound rather ominous.

    Below is crystalline magnetite with the readouts for you. I think your black sand ought to give you similar, although perhaps not identical readouts. You might want to check and see how your V3i responds for comparison sake………………….. Jim.

    Click image for larger version. 

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    Time, oh good, good time...where did you go?

  4. #34
    us
    Jan 2012
    Oregon Coast
    White's V3i, White's MXT, and White's Eagle Spectrum Cleangold sluice & prospectors pan, EZ-Gold Pan, and custom cleanup sluice.
    1,325
    1844 times
    Beach mining, Metal detecting, Trading.
    Hi Jim....
    Not sure how the cape really got it's name but this seems to be the recorded version.

    English fur trader John Meares names Cape Disappointment on July 6, 1788. - HistoryLink.org
    We hold these truths to be self-evident: that all men are created equal; that they are endowed by their Creator with certain unalienable rights; that among these are life, liberty, and the pursuit of happiness. Thomas Jefferson

    Which is also why we have the second
    amendment.

  5. #35
    ca
    Honorary Member of the Central Alabama Artifact Society (C.A.A.S)

    Jan 2008
    Canada
    F-75, Infinium LS, MXT, GoldBug2, TDI Pro, 1280X Aquanaut, Garrett ProPointer
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    Quote Originally Posted by TerryC View Post
    VERY NICE post, my friend. Informative and you do know the subject material! I have used my Gold Bug 2 for air tests many years now. I CAN use my hand to GB small samples using the GB2. The trick is (and many are not aware of this) that you can balance out the hand minerals as you would a sample. I cannot vouch for other detectors but after balancing my "hand salts" out, the GB2 will sound off on the smallest target in the hand. Good to hear from you again! ╦╦Ç
    Howdy Terry… thanks for dropping around and sharing your GB2 technique. I tried it on my GB2 and found that even at its minimum GB control adjustment, there was only a very modest loss of sensitivity to a half-grain lead nugget attached to a popsicle stick. It still signaled to it nicely at two inches or so. No worries, I ate the popsicle before doing the benchtest.

    I suspect my GB2 is a slightly different version from your unit because the minimum GB control adjustment only moderately reduced the positive signal from my hand. It suggests that my unit’s GB range is more limited. I bought it in Canada in 2010 so it’s probably an El Paso version. Also too, I know that increasing the threshold to maximum will not affect depth / sens in the discriminate mode, whereas I recall that technique worked with the original version.

    BTW, I used max volume / sensitivity, the “low mineralization” setting, and a 10” elliptical concentric coil to benchtest the Goldbug2, and max volume / sensitivity and 10” elliptical concentric for the F75.

    I had to reduce the F75’s GB control to GB ZERO to ground balance my hand. Even then, I can’t quite eliminate a slight positive signal. At GB45 and moreso with GB86, my hand produces a fairly strong signal. Now checking the half-grain lead nugget, the signal is much stronger at the GB86 and GB45 settings than it is at the GB ZERO setting.

    The GB ZERO setting produces a very slight (questionable) positive signal because the lead nugget was pretty well ground-balanced out. Obviously a salt range (GB ZERO) GB compensation point on the F75 is not a good choice to do a sensitive benchtest.

    Quite different results between my two units, it might be a good idea for interested hobbyists to run this test to evaluate how their own detector model responds at various GB compensation points to a tiny metal target.

    Thankyou very much Terry for your thoughts on the subject as they pertain to your Goldbug2. This is exactly the type of technical comment from a veteran nuggetshooter that I had hoped for when I posted this article.

    Jim.

    Click image for larger version. 

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    Time, oh good, good time...where did you go?

  6. #36
    ca
    Honorary Member of the Central Alabama Artifact Society (C.A.A.S)

    Jan 2008
    Canada
    F-75, Infinium LS, MXT, GoldBug2, TDI Pro, 1280X Aquanaut, Garrett ProPointer
    765
    1487 times
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    Quote Originally Posted by johnedoe View Post
    Hi Jim....
    Not sure how the cape really got it's name but this seems to be the recorded version.

    English fur trader John Meares names Cape Disappointment on July 6, 1788. - HistoryLink.org
    An excellent read that does clarify how the name "Cape Disappointment" came into existence and has survived alternate names from other explorers. Thanks William, it was a very captivating, historical article that renders my earlier surmise about a lack of safe haven / harbor as totally irrelevant....... Jim.

    Click image for larger version. 

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    gold tramp likes this.
    Time, oh good, good time...where did you go?

  7. #37
    Charter Member
    us
    Come out from under your bed today...... DO SOMETHING!

    Jun 2008
    Yarnell, AZ
    Ace 250 (2), Gold Bug 2, Tesoro Cortes, Garrett Sea Hunter, Whites TDI SL SE, Fisher Impulse 8, Falcon MD20, Garrett pinpointer.
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    I know my GB2 very well..... mainstay for the Stanton-Rich Hill area. I am still "learning" my newer Whites TDI SL SE. As you know, the TDI is a PI machine, a good compliment to the GB2. I hope to get expert instruction from Southern or another instructor of his caliber on a PI machine. I had a salesman at Outdoor Outfitters (Waukesha WI) give me a demonstration on the new F75 years ago. I found it a VERY sensitive machine but too much EFI from power lines at about 100 yards away. I passed back then. Tnx for responding, friend! ╦╦Ç
    Jim Hemmingway likes this.
    Now remember, when things look bad and it looks like you’re not gonna make it, then you gotta get mean. I mean plumb, mad-dog mean. ‘Cause if you lose your head and you give up then you neither live nor win. That’s just the way it is. – Josey Wales

  8. #38
    ca
    Honorary Member of the Central Alabama Artifact Society (C.A.A.S)

    Jan 2008
    Canada
    F-75, Infinium LS, MXT, GoldBug2, TDI Pro, 1280X Aquanaut, Garrett ProPointer
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    Quote Originally Posted by TerryC View Post
    I know my GB2 very well..... mainstay for the Stanton-Rich Hill area. I am still "learning" my newer Whites TDI SL SE. As you know, the TDI is a PI machine, a good compliment to the GB2. I hope to get expert instruction from Southern or another instructor of his caliber on a PI machine.

    I had a salesman at Outdoor Outfitters (Waukesha WI) give me a demonstration on the new F75 years ago. I found it a VERY sensitive machine but too much EFI from power lines at about 100 yards away. I passed back then. Tnx for responding, friend! ╦╦Ç
    Oh yes, my original F75 version is very much subject to erratic behavior in areas where EMI is present Terry. Hunting urban areas in zero discrimination is frequently impossible. Subsequent F75 versions have resolved the EMI issue, and Fisher has in the past offered an upgrade service to owners of earlier models as well. I didn’t bother with upgrading because there have been comments on the forums about loss of depth / sensitivity, and frankly I’ve been able to control my unit by adhering to a few simple procedures.

    I rarely use the stock 11” DD coil in urban areas because it invites EMI issues and is not nearly as sensitive as the smaller coils, and that includes the 10” elliptical concentric, to small stuff. In remote areas, my original F75 is normally as quiet as a churchmouse regardless which search mode or coil is used.

    In areas of problematic EMI, employ a smaller coil, and preferably a concentric coil. Concentrics are less prone to EMI (less windings / antenna effect) than are the DD coils I prefer my 6” elliptical concentric, and it is ideal for prospecting purposes. The depth is surprising on large stuff, and yet it is very sensitive to shallow small stuff less than a half-grain. Certainly not a Goldbug2, or other high frequency units on the tiniest of sub-grain pickers, but on the other hand it does go deeper on larger stuff.

    Of course for prospecting applications, the first option is to search in the motion all-metal mode. It is much less vulnerable to EMI than are any of the discriminate modes.

    If using a discriminate mode, avoid JE mode in EMI areas because it is extremely high gain, and therefore much more sensitive to EMI than are the DE or PF general search modes. If necessary, subsequently increase the iron discrimination and check how it behaves with the coil on the ground, not waving it around in the air. The coil on the ground normally settles it right down, but continue to increase iron discrimination until any erratic behavior settles down.

    I have never experienced any issue operating this unit anywhere when the above steps are employed. In fact I benchtest right in the house in the motion all-metal mode, normally with max sensitivity and small 6”elliptical concentric coil.

    As to your TDI SL Terry, I have the TDI Pro. The SL is more sensitive to small stuff whereas mine is used for much larger native silver hunting. Years ago I wrote an article describing how it is used here. A few years later, I upgraded that article to reflect my subsequent experience with it.

    Much of the information will apply to your unit, and you’ve nothing to lose by taking a few moments to read it. Ignore the section that compares the Garrett Infinium.

    Whites TDI Pro in Silver Rock Country (& Infinium Comparison) February 2011

    Jim.

    Click image for larger version. 

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    Time, oh good, good time...where did you go?

  9. #39
    Charter Member
    us
    Come out from under your bed today...... DO SOMETHING!

    Jun 2008
    Yarnell, AZ
    Ace 250 (2), Gold Bug 2, Tesoro Cortes, Garrett Sea Hunter, Whites TDI SL SE, Fisher Impulse 8, Falcon MD20, Garrett pinpointer.
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    Quote Originally Posted by Jim Hemmingway View Post
    Oh yes, my original F75 version is very much subject to erratic behavior in areas where EMI is present Terry. Hunting urban areas in zero discrimination is frequently impossible. Subsequent F75 versions have resolved the EMI issue, and Fisher has in the past offered an upgrade service to owners of earlier models as well. I didn’t bother with upgrading because there have been comments on the forums about loss of depth / sensitivity, and frankly I’ve been able to control my unit by adhering to a few simple procedures.

    I rarely use the stock 11” DD coil in urban areas because it invites EMI issues and is not nearly as sensitive as the smaller coils, and that includes the 10” elliptical concentric, to small stuff. In remote areas, my original F75 is normally as quiet as a churchmouse regardless which search mode or coil is used.

    In areas of problematic EMI, employ a smaller coil, and preferably a concentric coil. Concentrics are less prone to EMI (less windings / antenna effect) than are the DD coils I prefer my 6” elliptical concentric, and it is ideal for prospecting purposes. The depth is surprising on large stuff, and yet it is very sensitive to shallow small stuff less than a half-grain. Certainly not a Goldbug2, or other high frequency units on the tiniest of sub-grain pickers, but on the other hand it does go deeper on larger stuff.

    Of course for prospecting applications, the first option is to search in the motion all-metal mode. It is much less vulnerable to EMI than are any of the discriminate modes.

    If using a discriminate mode, avoid JE mode in EMI areas because it is extremely high gain, and therefore much more sensitive to EMI than are the DE or PF general search modes. If necessary, subsequently increase the iron discrimination and check how it behaves with the coil on the ground, not waving it around in the air. The coil on the ground normally settles it right down, but continue to increase iron discrimination until any erratic behavior settles down.

    I have never experienced any issue operating this unit anywhere when the above steps are employed. In fact I benchtest right in the house in the motion all-metal mode, normally with max sensitivity and small 6”elliptical concentric coil.

    As to your TDI SL Terry, I have the TDI Pro. The SL is more sensitive to small stuff whereas mine is used for much larger native silver hunting. Years ago I wrote an article describing how it is used here. A few years later, I upgraded that article to reflect my subsequent experience with it.

    Much of the information will apply to your unit, and you’ve nothing to lose by taking a few moments to read it. Ignore the section that compares the Garrett Infinium.

    Whites TDI Pro in Silver Rock Country (& Infinium Comparison) February 2011

    Jim.

    Click image for larger version. 

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    I will check out the reference, Jim. Tnx. Are you aware that my TDI SL is the very first TDI SL SE (special Edition)? I was told my SE version was the very first ordered.... before it was even advertised in the states. It seems (to me) that it may be an "experiment". Let's see where they go with it. Take care, my friend. ╦╦Ç
    Jim Hemmingway likes this.
    Now remember, when things look bad and it looks like you’re not gonna make it, then you gotta get mean. I mean plumb, mad-dog mean. ‘Cause if you lose your head and you give up then you neither live nor win. That’s just the way it is. – Josey Wales

  10. #40
    Charter Member

    Apr 2003
    Alberta
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    Jim,

    Really enjoy what you've posted here, and it's nice to see such a professional so willing to share your hard-earned knowledge with others. You sir are a detecting treasure in your own right. Many thanks.

    All the best,

    Lanny
    Nothin' quite as fun as chasin' sassy nugget gold! http://www.treasurenet.com/forums/me...mysteries.html

  11. #41
    ca
    Honorary Member of the Central Alabama Artifact Society (C.A.A.S)

    Jan 2008
    Canada
    F-75, Infinium LS, MXT, GoldBug2, TDI Pro, 1280X Aquanaut, Garrett ProPointer
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    Quote Originally Posted by Lanny in AB View Post
    Jim,

    Really enjoy what you've posted here, and it's nice to see such a professional so willing to share your hard-earned knowledge with others. You sir are a detecting treasure in your own right. Many thanks.

    All the best,

    Lanny
    Hi Lanny… thankyou for dropping around with those nice comments. It’s a good opportunity to acknowledge and thank some of the leading experts in the industry over the years for their help with technical information prior to posting such articles to the forums. In particular, Ty Brook of Alabama and Dave Johnson, Chief Design Engineer at First Texas. Both these individuals have reviewed some of my more technical articles and commented where appropriate. Dave added a few additional points of interest about pyroclastic material and its effects on ground phase readouts that were subsequently included into the report.

    I enjoyed writing the article, it was a lot fun to do all the mineral photography, benchtesting, and presenting the results. It also served as a diversion from the usual silver articles of the past, which was a refreshing change too.

    Benchtesting with a suitable metal detector provides today’s electronic prospector with a useful technique, no different than conducting other mineral tests such as specific gravity, streak, hardness, and so forth. We don’t use it often in our area, but it has a place in our toolbox, and it’s necessary to know how to do it properly. Hence we focused on distinguishing signals produced by iron minerals from those produced by non-ferrous material, for example the sulfide minerals that frequently indicate metalliferous prospects.

    I imagine you’ve been busy this summer. The wildfires in British Columbia have constantly been front-page mainstream news headlines over here in Ontario. We’ve had record wildfires in northern Ontario as well. I’ve been thinking about you over the summer, wondering how much the fires may have affected your gold hunting season. As far as I know at present, fires have not impacted the area I’ll be visiting shortly.

    Below is another example of generally common minerals. It came to me by swapping silver with an old friend from Alaska several years ago. But I can’t say that I’ve seen any examples of it in the silverfields of northeastern Ontario. I’m starting to run low on decent mineral photos to post here, but then this thread will soon have to be abandoned anyway. The wife’s retirement is next week, hence the unexpected delay, but afterwards we’re off to the north country until late October, then over to Bancroft for a week or two hunting crystals………………… Jim.

    Click image for larger version. 

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  12. #42
    ca
    Honorary Member of the Central Alabama Artifact Society (C.A.A.S)

    Jan 2008
    Canada
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    Hi Everyone... before abandoning this thread to head north prospecting for the autumn, I thought I’d leave you guys with the unidentified specimen below, and the following description. We don’t see this mineral in our search areas, but maybe you are familiar with it in your areas. I won’t say what I think it is to avoid influencing your ideas about its identity. I hope you will take your best shot at identifying it.

    ***********************************
    The mineral depicted below is documented in mining literature as occurring in ore veins as a gangue material, and otherwise it also occurs in pegmatites. Its pink / red color is a good clue to its identity if my ID is correct, and you should know that it is not garnet. Below are a few simple observations.

    The white background material won't scratch with a kitchen knife, but my workbench steel file did powder an edge slightly. As a point of interest only, the hidden side of the specimen is mostly a black rock-building material that ground balances on the F75 at GB90, but interesting that the Fe3O4 meter readout = ZERO.

    Using a 10X-30X-magnification loupe, I couldn't identify any crystal structure, but if my ID is correct, it does occur in beautiful crystalline form that is considered attractive and valuable. It has a vitreous or glassy luster, is translucent or even transparent. I'm not sure how to technically describe it, but the entire encrusted surface is rather rough and bumpy, although it can't be described either as granular or botryoidal.

    A steel nail scratches it but a copper penny will not mark it, indicating a probable hardness of about 3 ½ to 4. It also produces a white powdery streak. I didn't want to take a chisel to it, but I think it would be quite brittle and will easily fracture. Assuming that it has previously fractured to its current state, it can be described as uneven and somewhat conchoidal.

    That’s it for clues. I hope this “puzzle” will interest you, and that someone can identify it with confidence. I’ll return to this thread later in the season to see what you think about it and reply to you, thanks and good hunting………………. Jim.

    Click image for larger version. 

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  13. #43
    us
    Coil Swinger

    Jan 2011
    El Dorado County
    Minelab
    474
    453 times
    Rhodochrosite possibly laced with a little manganese and calcite in the mix?
    Will work for gold dust.

  14. #44
    ca
    Honorary Member of the Central Alabama Artifact Society (C.A.A.S)

    Jan 2008
    Canada
    F-75, Infinium LS, MXT, GoldBug2, TDI Pro, 1280X Aquanaut, Garrett ProPointer
    765
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    Quote Originally Posted by Gravelwasher View Post
    Rhodochrosite possibly laced with a little manganese and calcite in the mix?
    Hi Jay... it's pretty hard to argue with your identification. It agrees with mine and a knowledgeable friend and mineral / gold hunter from Alaska. You'd think the white material would scratch with a kitchen knife if it was calcite, but then I sometimes think that other small amounts of material in the mix can affect the hardness test. I've seen it with our silver / calcite samples.

    Interesting to practically realize that mineralogy isn't exclusively black and white, but rather there are many examples that don't necessarily fit into the "ideal" because of chemical substitutions or inclusions. Or at least that is what I think at present.

    Thanks for responding to this "puzzle" Jay. I didn't anticipate such an early response that would match our tentative identification. Now if anyone else has a possible alternative ID that might apply to this sample, please let us know, that's the idea behind the above post.

    Jim.
    gold tramp likes this.
    Time, oh good, good time...where did you go?

  15. #45
    us
    Coil Swinger

    Jan 2011
    El Dorado County
    Minelab
    474
    453 times
    Beautiful specimen Jim almost a ruby like quality to it!!
    A great photo really helped form a quick opinion on the sample posted.
    Much success on your prospecting trip!! More gold and minerals than dirt to you!!
    gold tramp and Jim Hemmingway like this.
    Will work for gold dust.

 

 
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