Detector screaming at pyritic vein material.

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goldshark

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While detecting, I detected a strong signal from an 8" dirty rock. First I washed, then sliced open said screaming rock with a large tile saw. The rock turned out to be vein material ( Quartz with mucho Iron pyrite stringers ), but no visible gold. I don't really want to crush this specimen, as it is a very good representation of local vein material. The small piece I cut off, set off the detector, so we crushed to 100 mesh, and panned it. Nothing but pyrite. I didn't roast, regrind, and pan again as I was really just trying to find the source of the tone, thinking it may have a small nugget trapped somewhere. So my question to more experienced detectorists is, when will a detector detect pyrites? Is it sounding off due to the ground balance detecting highly mineralized ground? My ground balance was fine tuned for a typical quartz ground, with some decomposed feldspars (clay), a little magnetite (fine), limestone, and migmatite being the 95% groundmass, with the occasional porphyry hot rock. I have detected some other ore piles of said quartz/pyrite, with no screams, same ground balancing, swing over said piece, and it screams. Does a bunch of fine pyritic gold add up to a small nugget? I am really trying to learn more about this phenomena of my GB2 detecting quartz/pyrite specimens, but no course Gold upon crushing to 100 mesh and panning. I have noticed this with many specimens I've detected and processed in above said fashion.
 
Ultra fine Gold in Pyritic and Gossanous material can be in quantities sufficient to register on a metal detector.
Most prospectors using Gold detectors here know little of Gold chemistry or Ultra fine Gold recovery and just label it as "hot rocks" and assume it's just iron if they can't pan colour from it

Cheers Wal
 
Here are some pictures of some gold and pyritic vein material I found with my detector. Everything in the photo, set off the detector ( except the tube of lip balm, only shown for size comparison ). Also note the color difference between the pyrite and the Gold. Yea, more grainy pictures of yellow rocks. I don't have a good enough camera to show the details I would like.
 

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goldshark said:
Here are some pictures of some gold and pyritic vein material I found with my detector. Everything in the photo, set off the detector ( except the tube of lip balm, only shown for size comparison ). Also note the color difference between the pyrite and the Gold. Yea, more grainy pictures of yellow rocks. I don't have a good enough camera to show the details I would like.
Click to expand...
I guess the big round rock contains appreciable amount of Copper ore. ;)
 
I'm running a Gold Monster 1000 and we frequently come across pockets of massive pyrites on our claims.
So far, the detector has never screamed at the pyrite content, only gold. I've often wondered why it won't read the pyrites and assumed that the programming is set up to ignore that response.
Having smelted a few batches of our sulphides, they do contain a small quantity of trapped gold, but not enough to detect.
 
goldshark said:
Here are some pictures of some gold and pyritic vein material I found with my detector. Everything in the photo, set off the detector ( except the tube of lip balm, only shown for size comparison ). Also note the color difference between the pyrite and the Gold. Yea, more grainy pictures of yellow rocks. I don't have a good enough camera to show the details I would like.
Click to expand...

Nice. Pyrites are sulfides, which react differently to electricity and electromagnetism...etc. I didn't think a metal detector would detect sulfide. With that said, there are probably sufficient hydroxides and/or oxides that are setting off the detector. The left rock could contain silver, lead, and other trace amounts of something else. The right side may be nickel, copper and something else.
 
Metal detectors, be they pulse induction or vhf, work by inducing a magnetic field in metallic objects.

It may seem strange but sulfides are not metal - kinda like water made of hydrogen and oxygen is no longer a gas - and doesn't burn either! If there is enough 'native' metal - perhaps very fine and disseminated - it will trigger a response in a metal detector - a hot rock. Most often magnetite.

Try a magnet on your sample - especially the fines. If no attraction to the original rock, or the fines after the magnetic portion is removed continues to trigger your detector, further interest is warranted.
 
Yatta, Yatta, Yatta, I know how to detect. Check out the nuggets below the said screaming pyrite specimens. Those nuggets made less noise than the 2 rock/ore specimens. I contacted, via youtube, and this forum, to hear that pyrite doesn't set off a tone. Bullshit ! As stated in my original post, pieces cut off from samples, contained no gold courser than 100 mesh. Are there any real detectorists out there? I know this is a refining forum, with a sub thread on detecting. I have already hit the other forums, and received the same comments. Maybe time to call Fisher. Thank you all.
 
It is true, that sulfides don't trigger metal detectors. I suspect no one has added another very important truth about sulfides; they don't block metal detectors from detecting metal contained therein - could be a nugget, could be very fine material. Your detector seems to be working properly as is your use of it. There is 'something' in your specimen that is NOT sulfide setting off the detector. No detectorist, or it's manufacturer, can tell you what that something is, based on how the detector behaves. Determining what you have requires physical processes such as pulverize, magnetic/ density/roasting separation, or smelting, or chemical analysis. You can pay experts to have such things done, or, you can decide which of the tests suggested to you, or found in your search for such, and seems simplist to you and begin there. Thusly, you might answer your question, or you can determine whether or not the sample seems worthy of the expense of professional testing.
 
goldshark said:
Yatta, Yatta, Yatta, I know how to detect. Check out the nuggets below the said screaming pyrite specimens. Those nuggets made less noise than the 2 rock/ore specimens. I contacted, via youtube, and this forum, to hear that pyrite doesn't set off a tone. Bullshit ! As stated in my original post, pieces cut off from samples, contained no gold courser than 100 mesh. Are there any real detectorists out there? I know this is a refining forum, with a sub thread on detecting. I have already hit the other forums, and received the same comments. Maybe time to call Fisher. Thank you all.
Click to expand...
Which detector are you using? Is it reading as a gold signal or something else? Have you tried multiple frequencies to get better discrimination? Sorry for all the questions just trying to cover as much as I can in a single post.

Ed
 
Last edited:
No worries guys and gals, this is what the forum is for. As stated in my original post, a roughly 2 pound specimen was cut from the piece on the left in the photo. It was a screamer, so it was crushed and ground to all pass 100 mesh. No + 100 mesh pieces where left on the screen, and no course Au was found on the screen. Panning to the sulfides revealed a little super fine Au. I didn't assay it, but still have the cons. The one thing I haven't taken in to account yet is the possibility of the semi oxidized rind of sulfides on the outer portion of the sample. Anyone know of that state of oxidized pyrite setting off a detector?
 
jobinyt said:
It is true, that sulfides don't trigger metal detectors. I suspect no one has added another very important truth about sulfides; they don't block metal detectors from detecting metal contained therein - could be a nugget, could be very fine material. Your detector seems to be working properly as is your use of it. There is 'something' in your specimen that is NOT sulfide setting off the detector. No detectorist, or it's manufacturer, can tell you what that something is, based on how the detector behaves. Determining what you have requires physical processes such as pulverize, magnetic/ density/roasting separation, or smelting, or chemical analysis. You can pay experts to have such things done, or, you can decide which of the tests suggested to you, or found in your search for such, and seems simplist to you and begin there. Thusly, you might answer your question, or you can determine whether or not the sample seems worthy of the expense of professional testing.
Click to expand...
He should try leaching. There's several acceptable methods. Then, extraction, and if PM residues result, part it--oxalic acid can be a good leaching agent for certain types of rocks-- I've used it on serpentine and schist, and can help as an addition to flux, especially for micro-fine gold.
 
Hey all, just going back to the original post. I know the rock specimens contain Gold, I am not disputing that. And I know how to crush, grind, float , leach, and refine the specimens. My question was why is my detector screaming at these specimens when there is nothing over 100 mesh Au in size? I did cut off a portion of the specimens, got a great tone off the detector, crushed to - 100 mesh, checked screen for oversize (none), panned and got a little flour Au. The cons did not set off the detector. Just wondering if anybody else has experienced this phenomenon.
 
That is what I was wondering, thank you for the explanation. The next question, is there a certain tenor of ore ( minimum amount of Au ) per ton, it takes to set it off? I am using a Fisher Gold Bug 2. The detector set off the large, pyritic piece, found at the surface, louder then a 1/2 gram nugget at 4 " burial depth. I doubt if anyone can answer that question, but thought I would throw it out there.
 

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