Are Gold / Silver Tellurides Detectable??

[Jim Hemmingway]

Hi Everyone,

I've read literature by well-known detector-prospectors, and completed a TreasureNet search on this topic. Such pretty much indicates that tellurides, for example calaverite or sylvanite... there are others too... are not detectable. But, there have been recent posts here and elsewhere that suggest tellurides are detectable.

How about posting your experience or thoughts on this subject for me. I'd certainly appreciate any helpful ideas or suggestions you could share with me. I have no sample to test, but needless to say I don't mean tellurides that obviously show native gold or silver on their surface. Thankyou, looking forward to your replies.

Jim.

 

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[IMPDLN]

I am going to respond just to bump this post back up the list as this is a very good question from Jim, and I have not got the answer. However I would also like to know. Great question Jim. Dennis

 

[DDancer]

I dont see why some tellurides would not be detectable. Some pyrites, for example, are detectable. It would just depend on the ratio of sulfide to pure metal is in the material as well as how cohesive the metal is in the specimen. As a rule sulfides are not detectable so would such a find be considered a telluride or a specimen of the base metal detected?

 

[DDancer]

Sorry for the double post but people tend to loose interest after the initial read and an edit would get lost. Anyrate I was picking around and came across an interesting thread in Steve Herschbach's site, detectorprospector, in his rocks forum on Gold tellurides that might be of interest. Had me scratch my head but its an interesting read.

 

[Assembler]

Have talked to some who suggest taking a older anolog type gold detector and null tuning the detector on the sample it self to "Null out all the background iron" then slowly turn the rock sample. The idea is to tune the detector to cut out all the background iron before the actual metal detecting. Best to use the smallest coil you can as well.
Some times there can be a "Pocket of values" inside the surrounding material. The question is the "Pockets" big enough to metal detect very easy?
Some old timers and rock books refer these "Pockets" as "Birds nests" etc.

 

[Jim Hemmingway]

Thanks Dennis, DDancer, and Assembler for your replies to this topic. A similar thread on Steve’s Detector-Prospector forum motivated me to open this topic to discussion here. On Steve’s forum I’d suggested the comparison to iron pyrites as well. Plus we might expect that some telluride samples contain native silver or gold within the ore structure.

I have two half-dollar size pyrite samples, and one fist-size pyrite sample. Only the one half-dollar size sample does not respond to a metal detector. It is not a well-structured cubic crystalline sample but more a loosely botryoidal lump of iron pyrite. Does that account for the lack of signal? I simply don’t know the answer to that question, and don’t want to ruin the sample to find out.

The fist-size iron pyrite sample, pictured below, produces a very strong benchtest signal even at GB45 on my F75, which I think is roughly equivalent to the metal / mineral “null-point” that can be set on older analogue VLF detectors as alluded to by Assembler. At that GB setting, all of the various types of naturally occurring oxidized iron mineralizations including troublesome maghemite do not generate a positive response in a benchtest, at least not in my experience. At the F75's GB45 setting the detector is considerably less sensitive to any metal target in a benchtest than it would be at a less conductive GB point such as the high GB80s typical of northeastern Ontario's prospecting country. But even at the GB45 point, two of my pyrite samples signal very well, as does the arsenopyrite sample depicted below. In fact that goes for the larger, massive galena samples occasionally detected in the silver producing areas we hunt. Smaller galena / arsenopyrite samples of comparably indeterminate structure do not produce a field “in-situ” signal at all.

​

So it seems to relate to structure / possibly sample size, and obviously to native metal content within the pyrite or telluride. I commented on Steve’s forum that tellurides free of any native metals could be assumed to either be non-conductive or possibly marginally conductive similar to iron pyrite. That was about the best hypothetical comparison that occurred to me at the time.

It is also true, as DDancer points out, that many sulfides are not detectable. And yet we know that the examples noted above, several of the copper sulfides, and our plentiful iron sulfide named ‘pyrrhotite’ are good examples of sulfides that can and do produce solid metallic type signals. In fact pyrrhotite, when in a reasonably solid structure, blocks PI electromagnetic field penetration completely. Could this be an additional factor however remote, whereby some tellurides contain some measure of detectable sulfide material? In other words, was there sulfur within the ore's matrix?

In any event, I do not dispute that some electronic prospectors have detected telluride samples. The purpose of this thread was to learn more about the subject. Thankyou for your thoughts and for breathing some life into this thread, hopefully we’ll hear more from detectorists who operate in areas known for their telluride production / occurrences.

Jim.

 

[Assembler]

Between the crystals on both the arsenopyrite and the iron pyrite there could be some values. Again the question is the values easy to metal detect? How much?

 

[UncleMatt]

I think gold tellurides often have free gold particles or pieces in their matrix. Of course not always, but often. And such free gold would definitely be detectable with a metal detector, as long as it was large enough to be sensed by the detector in question.

 

[DDancer]

Assembler, as to how easy any values would be detectable try looking at it this way. Depending on the detector your using, VLF/PI/ZVT technology, any material being detected would have to have enough solid metals, non-sulfides, to produce a return signal for the detector. There are plenty of accounts of "invisible" gold, usually specimen or porous gold, that are being detected successfully with one type of technology or another. My thought is just how disseminated solids are in a given specimen to produce a BEEP. I feel the same thought holds true for pyrites, silver and other metalic sulfides or even chlorides. Jim has some impressive threads on his silver prospects and in reading them I've often been drawn to the same thought.

 

[ecmjamsit]

Metal detectors will not work for tellurides. Tellurides are an alloy that that does not provide enough change in inductance to the coil. Tellurides do not provide a counter electromotive force for pulse induction machines. The only technology to detect a surface telluride is x-ray fluorescence machine. They go for $20K plus!

https://www.thermofisher.com/order/catalog/product/XL3TGOLDDPLUS

 

[Assembler]

Metal detectors will not work for tellurides. Tellurides are an alloy that that does not provide enough change in inductance to the coil. Tellurides do not provide a counter electromotive force for pulse induction machines. The only technology to detect a surface telluride is x-ray fluorescence machine. They go for $20K plus!

https://www.thermofisher.com/order/catalog/product/XL3TGOLDDPLUS

A rock saw may help one to 'See' if there is any values between the tellurides or pyrites. The amounts may be so small as to only be seen by a lens. However once in a while may be big enough to metal detect at close range.
The $20K plus is not in most peoples price range. However is interesting.

 

[Jim Hemmingway]

Metal detectors will not work for tellurides. Tellurides are an alloy that that does not provide enough change in inductance to the coil. Tellurides do not provide a counter electromotive force for pulse induction machines. The only technology to detect a surface telluride is x-ray fluorescence machine. They go for $20K plus!

https://www.thermofisher.com/order/catalog/product/XL3TGOLDDPLUS

What little information is available in the literature does agree with ecmjamsit’s response that (given the absence of other detectable substances such as native metal within the structure) tellurides are not detectable. Both Jim Straight’s Prospecting Eluvial Placers with a Metal Detector, and Charles Garrett’s Modern Electronic Prospecting suggest that tellurides are not detectable in the field.

Tellurides are similar to sulfides, and are usually classified with them in mineralogical texts. My understanding is that gold telluride such as calaverite is not an alloy or amalgam of gold and tellurium, but rather it occurs as a result of a chemical reaction, creating a distinctly new, brittle chemical compound. No different in that respect than sulfur and iron falling out of solution and forming any one of several iron sulfides such as iron pyrite, pyrrhotite, or marcasite as good examples. As a general rule of thumb, I don’t consider iron pyrite to be a field-detectable substance, whereas we know that pyrrhotite strongly qualifies as such, regardless of the detector technology utilized. So again, perhaps it comes down to how the mineral is formed structurally.

The difficulty with photographic evidence to support the notion that tellurides are field-detectable is that the few photos I’ve seen appear to have other material within the matrix that may have produced a signal. Or for example, an occasional “roasted” sample that appears to have residue sulfur on the surface pretty much disqualifies it from consideration as a telluride to my way of thinking.

I suppose it is good to know this background information and hypothesize, but unfortunately it doesn’t really put us any further ahead in understanding whether pure tellurides can produce a detectable signal. A few hobbyists say yes while others say nyet.

So we may not settle firmly on a definitive answer here, although I’m inclined to agree with ecmjamsit’s unequivocal post. But if nothing else, at least we’ve gained some additional exposure, via our discussions, about how various, similar minerals commonly encountered in the field may or not react to metal detectors, keeping in mind that benchtest results do not necessarily duplicate what happens in the field.

And as a bare minimum through our discussions, we’ve become a little better acquainted here on this forum, which is no trivial thing… thanks to everyone for your contributions to date.

Jim.

 

[ecmjamsit]

The problem is you are try to detect a material using electromagnetic waves. The primary tellurides of North America are sylvanite, calaverite and petzite. The element tellurium is a metalloid. It is in between the metal and non metals. You have to remember tellurides are crystals. They always appear in a crystalline form. So you have an alloy of gold and silver combined with the metalloid tellurium. The tellurium spoils the inductive properties of the gold and silver by dispersing their atoms in such a way that common metal detectors won't respond. Researchers might be able to develop a "telluride detector" one day. I would speculate it would involve using a specific frequency of radio energy and would only detect a telluride from an impractical distance.

If you had a lot of money, you could have a laser zap a target. The resultant decomposition could be spectrometrically analyzed for Au, Ag and Te. I believe NASA has done this with some of their exploratory spacecraft. A person would have to be an expert in crystallography to detect tellurides with a sensor i.e. metal detector. I hope this inspires others!

 

[Assembler]

The problem is you are try to detect a material using electromagnetic waves. The primary tellurides of North America are sylvanite, calaverite and petzite. The element tellurium is a metalloid. It is in between the metal and non metals. You have to remember tellurides are crystals. They always appear in a crystalline form. So you have an alloy of gold and silver combined with the metalloid tellurium. The tellurium spoils the inductive properties of the gold and silver by dispersing their atoms in such a way that common metal detectors won't respond. Researchers might be able to develop a "telluride detector" one day. I would speculate it would involve using a specific frequency of radio energy and would only detect a telluride from an impractical distance.

If you had a lot of money, you could have a laser zap a target. The resultant decomposition could be spectrometrically analyzed for Au, Ag and Te. I believe NASA has done this with some of their exploratory spacecraft. A person would have to be an expert in crystallography to detect tellurides with a sensor i.e. metal detector. I hope this inspires others!

Interesting that the tellurides such as sylvanite, calaverite and petzite have to be in crystal forms. In between the crystals can be anything including some values. One question to maybe look at is there a difference between the three such as sylvanite, calaverite and petzite that one type may have bigger spaces between the crystals that could have some conductive material enough as to react with a metal detector coil?
Could two identical gold detectors with say 4" coils with the sample target material between respond in 'Locking clock signal of both detectors' detect small amounts of conductive value material between the crystals? Just don't know. Anyone try this?

 

[Jim Hemmingway]

The problem is you are try to detect a material using electromagnetic waves. The primary tellurides of North America are sylvanite, calaverite and petzite. The element tellurium is a metalloid. It is in between the metal and non metals. You have to remember tellurides are crystals. They always appear in a crystalline form. So you have an alloy of gold and silver combined with the metalloid tellurium. The tellurium spoils the inductive properties of the gold and silver by dispersing their atoms in such a way that common metal detectors won't respond. Researchers might be able to develop a "telluride detector" one day. I would speculate it would involve using a specific frequency of radio energy and would only detect a telluride from an impractical distance.

If you had a lot of money, you could have a laser zap a target. The resultant decomposition could be spectrometrically analyzed for Au, Ag and Te. I believe NASA has done this with some of their exploratory spacecraft. A person would have to be an expert in crystallography to detect tellurides with a sensor i.e. metal detector. I hope this inspires others!

Ecmjamsit… I took a similar position over on Steve’s forum re: crystalline structure, chemical bonding via electron exchange between gold and tellurium, and so forth. But much the same can be said about those two sulfide specimens depicted in the photos posted above, both are highly crystalline and both generate a good benchtest signal to a mid-frequency F75 using a (less sensitive) GB45 setting in either motion all-metal or discriminate modes. However both those samples could harbor sufficient native metal to help produce those good signals. We’ll never know for sure.

Now don’t misinterpret my words, because I do agree with you, and certainly do not question your knowledge. I don’t see how a telluride could be any more likely to produce a signal than commonplace iron pyrite, which usually is not field-detectable. In fact smaller pieces are normally not detectable even in a benchtest.

It is interesting that nobody contributing to this thread has suggested that tellurides (in the absence of native silver or gold inclusions) are detectable. I think we can interpret that as a consensus.

Assembler… I think we generally agree that any interstices that exist between crystals could accommodate the presence of conductive native metal such as gold or silver. Based on examples regularly posted to the forums, we can readily see that it would take only a tiny amount of flattened gold or silver to generate a signal from a high frequency VLF unit such as a Fisher Goldbug2.

Jim.