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7 Days Of Arizona Detecting With The 6000


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An XRF (spectrometer) 'gun' in the hands of someone who both a) knows how to operate it properly and b) knows how to interpret the big picture it helps paint in a geological sense.  Throw in c) -- a forum member and contributor -- and you've got the trifecta.

There's more to this site than eye candy, but I like that too.

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Thanks for reading and the comments everyone!

16 hours ago, IdahoPeg said:

I had a few episodes of squirrelly emi in Nevada but plan to hunt Arizona next winter…not looking forward to an increase in emi!

The issue, near as I can tell at this point, seems symptomatic of both something in the machine as well as the local environment combined. I used two different machines in NV and AZ, and I wonder if some machines might be more affected than others? I'm unsure...but hopefully yours runs smoothly here! 

14 hours ago, Glenn in CO said:

Like to hear more on your exploring tips on how you decide on areas you want to detect. Thanks for sharing,

This area was a bit different than what I normally do, this trip I owe the chance to get here all to a fellow forum member. I was investigating a fairly small area that was already known for gold but has a number of plausible theories as to where it came from, and I love those kind of mysteries. This trip was sort of a "shotgun pattern" in a specific area just to see what did and didn't hold gold and to take some rock and soil samples. I say exploration since it's fairly new to me and I'm trying to recreate the picture from scratch, but it's been very well detected in the past compared to the places I normally go. 

1 hour ago, GB_Amateur said:

An XRF (spectrometer) 'gun' in the hands of someone who both a) knows how to operate it properly and b) knows how to interpret the big picture it helps paint in a geological sense.  Throw in c) -- a forum member and contributor -- and you've got the trifecta.

Thanks, I'm definitely still learning though. I need to get a 2nd mining calibration recalibrated specifically for a quartz matrix for more accuracy I think, and probably a 2nd soils calibration with more heavy elements added, and one metals calibration specifically for shooting gold nuggets in specific rather than using the precious metals one, but they are pricey to do right now. I think I get some erroneous readings since my calibrations are more general rather than calibrated for known specific matrix materials, so I'm not fully trusting the readings but more using them qualitatively or for rough ideas at this time.

I have one heck of a story about how XRF can give some spurious readings even when done by "the pros". It's caused me to ignore gold entirely in the mining and soil calibrations, and also there is zero % chance I'd ever pay for an assay that uses an XRF finish now too. Anyways, that may be a story for some other day. 😀 I find the XRF really informative and useful just to shoot rock and soils and look for tracer elements quickly and on site though. There are actually 3 tracer elements I'm finding in common so far - cobalt, titanium, and niobium. Ti is a (somewhat) common rock forming element or inclusion, but the cobalt and niobium are not not common or present in other surrounding rocks and so might be useful to trace the path of an ancient channel and find a source. Plus they aren't as susceptible to spurious readings on the XRF as some other elements like gold, so I have a higher confidence in their accuracy. Also, niobium to me potentially suggests a pegmatite somewhere and/or maybe some rare earths, of which I'd also need to get a new calibration for.

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Wow Jason, great post and love your pimped-out ATV! So your swinging the GPX 6000 now...yep a truly easy, lightweight, gold-finding detector and I love mine. Was wondering if that monster nugget Gerry posted from AZ in 2021 was found by you???😮

Bill

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4 minutes ago, cobill said:

Wow Jason, great post and love your pimped-out ATV! So your swinging the GPX 6000 now...yep a truly easy, lightweight, gold-finding detector and I love mine. Was wondering if that monster nugget Gerry posted from AZ in 2021 was found by you???😮

Bill

Haha thanks, I love that side by side. I got a 50w solar panel up top, a lifepo battery behind the seat, inverter, mounts for many detectors, rock hammers, picks, pry bars, shovels, claim stakes, and everything else a prospector would need for an expedition! Got an ammo can just for shackles, slings, and other stuff just to pull boulders (or pull myself out of a ditch). Another ammo can just for chisels, hand scopes, streak plates, sample bags, hardness tester picks, etc. It's a modern prospecting chuck wagon!

Definitely wasn't me who found the nugget. 🙂 I can wish though... If I had to guess I would guess Mexico right now. But it definitely could be an AZ lump as the two places have some very similar looking gold.

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Thanks for sharing your adventure. I'm curious what brand of XRF detector you are using? When I was doing base metal exploration for a living the must-have piece of gear was Thermo Fisher's NITON portable XRF (a cool $40k circa 2010) but prices have now come down a lot. What it was not good at was giving real numbers for cobalt in iron rich environments. The problem is that the cobalt XRF peak is right next to the iron peak and the software couldn't tell whether it was reading a cobalt signal or the shoulder of the iron bell-curve.

https://www.olympus-ims.com/en/insight/the-fault-with-cobalt-overcoming-the-challenges-of-battery-metal-exploration/#:~:text=XRF is prone to inter,for XRF to ID cobalt.

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1 hour ago, jasong said:

Thanks, I'm definitely still learning though. I need to get a 2nd mining calibration recalibrated specifically for a quartz matrix for more accuracy I think, and probably a 2nd soils calibration with more heavy elements added, and one metals calibration specifically for shooting gold nuggets in specific rather than using the precious metals one, but they are pricey to do right now. I think I get some erroneous readings since my calibrations are more general rather than calibrated for known specific matrix materials, so I'm not fully trusting the readings but more using them qualitatively or for rough ideas at this time.

I have one heck of a story about how XRF can give some spurious readings even when done by "the pros". It's caused me to ignore gold entirely in the mining and soil calibrations, and also there is zero % chance I'd ever pay for an assay that uses an XRF finish now too. Anyways, that may be a story for some other day. 😀

You have the attitude of a (good) scientist.  Wonder why that is....  😁  Calibration and consistency checking are so important but along with things like statistics, are seldom taught in beginning and intermediate (even many advanced) classes.

OK, I'll include a side story which illustrates some of the points you are aware of.  On a particular popular current cable TV show (which I won't name to hopefully avoid the usual vindictive attacks) they've been using an XRF gun to determine the presence of precious metals.  Of course they are looking for gold and silver, but the spectral analysis shows many more elements.  Consistently (well, at least on a small handful of screenshots I've seen) their list shows considerably more Iridium than gold!  Yet iridium is not only rarer, but would likely only be found if naturally occurring in their location whereas gold (it is hoped) is from hidden treasure.  So what's up?   Of course they never mention this anomaly; I don't think it's because they are trying to bury it but rather due to a) they aren't focused on that element, and b) they don't really understand their instrument.  (Hopefully it's not because their instrument is improperly calibrated, using improperly written software, etc.)

(Now I'm getting a bit technical, but hopefully at least the gist of this is understandable by most readers.)  The innermost electron shell of atoms -- the most tightly bound and thus the most energetic -- is called the K-shell.  The second innermost shell (less energetic electrons) is the L-shell.  In some cases there is a near overlap of high atomic number elements (such as gold, platinum, lead) L-shell electrons with the K-shells of lower atominc number elements such as copper and zinc.

Because of the way an XRF spectrometer works, specifically when under a certain calibration, only a part of energy space is viewed.  In this (TV show) case it is viewing around the 10 keV energy region which is where those heavy element L-shell emissions lie, and also where some of the lower atomic weight metals' K-shell emissions occur.  As a specific (and pertinent here) case, Iridium's L-alpha line energy is 9.175 keV and Copper's K-beta line is 8.905 keV.  That's pretty close (<0.3 keV separation) and I hypothesize the instrument is interpreting a copper signal as an Iridium signal, leading to a spurious report.

The problem here comes down to whether or not the gold signal is from gold or a low atomic number common metal.  It probably does indicate gold, but IMO it requires more than just accepting the simple (and in this case tiny) XRF signal.   It appears to be a classic case of confirmation bias.

There are ways around this ambiguity, for example in the case of L-lines, requiring presence (and thus a coincidence) of both L-alpha and L-beta lines, which are (in the case of the heavies) sufficiently separated in energy (e.g. 1.5 keV separation for Iridium) to be resolvable.  I would hope the instruments use this technique, but it doesn't appear to be the case for the one in use on that TV show.

 

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35 minutes ago, Off Grid said:

Thanks for sharing your adventure. I'm curious what brand of XRF detector you are using? When I was doing base metal exploration for a living the must-have piece of gear was Thermo Fisher's NITON portable XRF (a cool $40k circa 2010) but prices have now come down a lot. What it was not good at was giving real numbers for cobalt in iron rich environments. The problem is that the cobalt XRF peak is right next to the iron peak and the software couldn't tell whether it was reading a cobalt signal or the shoulder of the iron bell-curve.

https://www.olympus-ims.com/en/insight/the-fault-with-cobalt-overcoming-the-challenges-of-battery-metal-exploration/#:~:text=XRF is prone to inter,for XRF to ID cobalt.

I have a Oxford Xmet 7500, it was a demo unit for a dealer I bought used so it comes with every method they offered at the time. I paid $15k for it, which was quite a deal given the amount of methods it came with. It doesn't have a Geochem method, but it does have a specific method for cobalt that I believe has an algorithm to differentiate from the iron peaks. The problem is the cobalt method doesn't have as many elements as the mining or soil methods installed, so that's why I want to send it back to the factory for recalibration for soils/rocks specific to what I'm looking for. For instance to be able to have high accuracy for cobalt in gravels/soil with high iron content too. The problem is...what I'm looking for always changes. 😀

I can definitely see "bleedthrough" when looking at gold with other elements with similar peaks too, Hg, Pt, etc. It's a Rhodium anode so I thought it'd be better for gold but it's still not accurate enough for me to take gold readings seriously unless it's like maybe 1000ppm or higher. But at that point I could probably see gold in ore with a loupe and bare eye, so... 

All of this kind of stuff is why I only use the XRF specifically qualitatively and not quantitively myself. For instance, with cobalt, if it's under like 50-100ppm I'll probably still ignore it as potentially spurious. And higher readings I don't really take the numbers specifically, I just look at it more like a "present/not present" element indicator. 

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42 minutes ago, GB_Amateur said:

You have the attitude of a (good) scientist.  Wonder why that is....  😁  Calibration and consistency checking are so important but along with things like statistics, are seldom taught in beginning and intermediate (even many advanced) classes.

OK, I'll include a side story which illustrates some of the points you are aware of.  On a particular popular current cable TV show (which I won't name to hopefully avoid the usual vindictive attacks) they've been using an XRF gun to determine the presence of precious metals.  Of course they are looking for gold and silver, but the spectral analysis shows many more elements.  Consistently (well, at least on a small handful of screenshots I've seen) their list shows considerably more Iridium than gold!  Yet iridium is not only rarer, but would likely only be found if naturally occurring in their location whereas gold (it is hoped) is from hidden treasure.  So what's up?   Of course they never mention this anomaly; I don't think it's because they are trying to bury it but rather due to a) they aren't focused on that element, and b) they don't really understand their instrument.  (Hopefully it's not because their instrument is improperly calibrated, using improperly written software, etc.)

(Now I'm getting a bit technical, but hopefully at least the gist of this is understandable by most readers.)  The innermost electron shell of atoms -- the most tightly bound and thus the most energetic -- is called the K-shell.  The second innermost shell (less energetic electrons) is the L-shell.  In some cases there is a near overlap of high atomic number elements (such as gold, platinum, lead) L-shell electrons with the K-shells of lower atominc number elements such as copper and zinc.

Because of the way an XRF spectrometer works, specifically when under a certain calibration, only a part of energy space is viewed.  In this (TV show) case it is viewing around the 10 keV energy region which is where those heavy element L-shell emissions lie, and also where some of the lower atomic weight metals' K-shell emissions occur.  As a specific (and pertinent here) case, Iridium's L-alpha line energy is 9.175 keV and Copper's K-beta line is 8.905 keV.  That's pretty close (<0.3 keV separation) and I hypothesize the instrument is interpreting a copper signal as an Iridium signal, leading to a spurious report.

The problem here comes down to whether or not the gold signal is from gold or a low atomic number common metal.  It probably does indicate gold, but IMO it requires more than just accepting the simple (and in this case tiny) XRF signal.   It appears to be a classic case of confirmation bias.

There are ways around this ambiguity, for example in the case of L-lines, requiring presence (and thus a coincidence) of both L-alpha and L-beta lines, which are (in the case of the heavies) sufficiently separated in energy (e.g. 1.5 keV separation for Iridium) to be resolvable.  I would hope the instruments use this technique, but it doesn't appear to be the case for the one in use on that TV show.

 

You are probably right. I haven't seen that TV show, but I've seen similar results.

I own a property that in fact does have iridium (as well as all 5 other PGE's). I decided to search for the source since they show up in AAS in the black sands. I thought I found the source, my XRF showed both Ir and Pt. I sent rocks in for assay, and they confirmed PGE's in the host rock. They confirmed it in...well...suspiciously similar quantities as my XRF showed, even though they said they were not using XRF for assay.

I ended up buying my own assaying equipment and teaching myself to assay because I didn't trust these lab results. And I was unable to reproduce the gold results from either lab after a month of trying and probably 30 or 40 attempts.

Well, many other things happened. And long story short - I think that maybe 2 labs are actually using (and misinterpreting) XRF results either in the finish, or just as a total shortcut for their PGE assays, and I think maybe for their gold assays as well. I wasted a ton of time and money on that. I finally spent the money and waited the 2 months to send my samples off to the same lab that Barrick, Newmont, etc are using in Nevada, and it confirmed my suspicions.

The last lab was expensive. But they had proper chain of custody and complete documentation for each step of the assaying process, plus they had lab controls that I could go back and check. And I will NEVER. NEVER. use a cheap lab again, only professional labs for assays for me from now on. Expensive lesson I learned.

I won't ever use XRF as a substitute for a real assay. I just use it as a quick field tool to gather data and samples to send in to a proper assay lab.

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Great story and cool RZR prospecting rig!

I do feel there is a problem with the GPX-6000 noise. I am using headphones and the EMI seems to build as you use the machine and eventually resort to a factory reset. I feel the noise build-ups rob the machine's depth.

-Don

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