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Hard Rock Tailings Vs Placer Tailings


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I had posted the following in another thread recently but it did not get much traction maybe because the thread was about something totally different? LOL 

If you have an opinion let's hear it! This thread is not titled for experts only!

 

On 3/25/2016 at 8:04 PM, argyle said:

Discounting general un-dug hardened ground, and concentrating on the type of 'pushed material in the form of broken up tailings you mention like Ganes Creek (I've never been there of course) and detecting the big un-pushed high tailing piles (we call them mullock heaps)...

I wouldn't take my PI at all. No advantage over VLF's in these scenarios whatsoever. Simply leave it at home, and take your pick from from any VLF unit that can really punch the gain through tailings, and run an 11" round and up, preferably 13" and larger.

 

I wonder if there is a difference in performance in tailings depending on the type of tailings. Do we need to differentiate between hard rock tailings and placer tailings when talking about the relative merits of PI versus VLF. For instance tailings from ancient river deposits as opposed to a hard rock tailings deposit consisting of iron rich ultra-mafic rocks. Or is it a moot point in all ground types of hard rock tailings due to no electrical conductivity in hard rock tailings because they are busted up? I think quartz tailings can be very benign almost to the point of an inability to GB on them.

In regard to depth on tailings  between PI/VLF being basically equal, is that true in all instances except for say a GPX or GPZ due to the battery power enabling a much higher level of gain? Like VLF = TDI but VLF < GPX?

HH,

Merton

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I thought argyle answered that question already, Of coarse some rocks will effect both types of detectors, Serpentine will make a VLF moan like the Mother In law and hot and cold rock will effect both types of machines, with the TDI you can adjust the GB or the Delay and make some rocks Vanish, Again with Mullock heaps / Tailing Piles because the ground matrix has been disturbed / broken up what you are in fact detecting over is many smaller versions of the ground when they were all as one, not only that they are now residing in their new location But they are not part the matrix in that area, Not only that when the rocks were joined as one their matrix was all  part of the original area so what ever property's they had are now mixed up with some lesser mineralized rock and some higher remembering that they are no longer part of the ground/Earth because now they are Sitting On It surrounded by Air Pockets etc.

john

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Thanks for the reply John. And you are correct, Argyle responded to this question in the other post. But if each question posted on this prospecting forum only received or needed one reply for there to be a definitive answer to the question then this forum would be a pretty dull place. So much of the content here is just our opinions not fact. Everybody sees things in a little different light so the larger amount of opinions posted gives readers a greater chance to learn and form there own opinion or modify a previous belief they held.
At times if I post a question I already have my own opinion/belief/answer. I post the question to spark discussion, which in turn taps into the vast store house of metal detecting knowledge members of this forum possess. I hope to learn something from each answer posted and hope others can too. This post actually asks two questions. One about different types of tailings and the mineralization therein. How a detector may react to hot rocks in the matrix, rapidly changing ground from different parts of the dump, even coil selection between placer(many cobbles) or hard rock(often way smaller, uniform material) could be topics of discussion. The second question is the old PI versus VLF debate focusing on performance differences on tailings. Plenty of room here for discussion and learning if members avail themselves of the opportunity. 
This is Steve's forum but without active participation from it's members it will wither and die, cease to be one of the best MD forums on the net. So I will ask again- if you have an opinion please take the time to post it.
HH,
Merton

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I the past when some large rocks have been a pain I have actually Ground balanced on them it does not eliminate them completely but it does lead to a quiet life with a VLF and you will still get a slight rise in the threshold when you go very close to them or as you pull the coils away depending if your GB is set slightly positive or slightly negative, But this is where Good coil control comes in, You can tell a lot about how good A detectorist is just by watching their coil control,, I remember one guy with a DFX using a 20 coil and He really Loved him self, But when I watched him use his machine he was swinging it like a pendulum and not only that even if he had of kept it level the speed he walked at he was missing about 90-95% of the area that he had walked maybe more.

If you can when you do find some nasty rocks try and find a nice flat one and take it home because the you can place test bits on it and try out some settings on how to deal with them in the field, you can even put them in a test garden and bury targets around them to simulate real world detecting,.

Hope this helps,  John

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goldbrick

 It's Steve as always can help you more on that question than anyone. This being he's had a claim like that and done that type of detecting. I know on some of the other forums like Rob Allison has been to Moore creek and I understand it's like Gains Creek. I just know it was all about hunting tailings from a dredge in pass years.

Chuck

 

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I've only had experience hunting drywash tailing piles here in Arizona and I've had pretty good luck with them using my GPZ. I found a nice "pebble" specimen that weighed a few grams that I'm assuming was too spongy and deep for VLFs and PIs in the past because this was a pounded area. The GPZ is the king of specimen gold.

I've had other luck in drywash piles with the GPZ on tiny gold nuggets that were too deep and small for other detectors. 

My favorite experience is finding a really old drywash pile that no one else knew was a drywash pile because it was flattened and covered by a layer of dirt. It won't be the typical pile of pebbles. I've made some nice finds in situations like that. I'll hear a target and start digging and once I'm thru the first few inches of soil it's nothing but pebbles and I know I'm on an old, hidden tailings pile. 

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I think that Ganes cr was mild to Moore cr.  I never been to Moore cr, but as other friends of mine have been to Moore cr.,they said that the tailings at Moore cr had more minerals in them than Ganes cr. I hunt other tailing piles and Ganes cr was easier to hunt. I also hunt old mine tailing piles and those with sulfides mask the gold, unless it is large pieces. I have used a VLF detector and a PI detector on both types of piles. 

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I and my wife have been most productive detecting hard rock tailings for more than twenty-five years. Both the VLF and PI have there place when detecting for gold in mineralized  and low mineralized tailings, but the type of detector used for the type of gold  you are seeking also must be consider. A VLF will usually detect all types of gold in low to somewhat hot ground with a limit to depth that can be achieved depending on the size and weight of the gold. A PI will detect gold at greater depths than a VLF, but it will not detect all types of gold. It comes down to using the right detector for the area and gold you are seeking. In my opinion there is no detector available today that can be used for all conditions that one would encounter at in the field.

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1.
I wonder if there is a difference in performance in tailings depending on the type of tailings. 

Difference in say one single detectors performance? in direct regard to different make up of the rock matrix on types of tailings...
I'd say not by much of a margin consistently overall. As most piles are benign and quiet to both VLF and PI.
Then you come across a tailing pile/mullock heap that carries within it large chunks of nicely cooked heavy ironstone that shuts most detectors down. 
Or a large amount of heavily localised 'hot' shale, whether yellow or red shiny liver ect. Then the difference in performance can be extreme, and the fun begins in choice of which unit or type of unit to use.
But these are not the vast majority of tailings.

2.
Do we need to differentiate between hard rock tailings and placer tailings when talking about the relative merits of PI versus VLF.

I definitely think so Merton.

Hard rock mullock for me has nearly always produced quieter and deeper detecting, ...as opposed to re-working dirt from sluiced workings, especially if they contain high mineral conglomerate.
But again, I feel there is no overall winner between VLF and PI as each individual pile will have it's own mix.

3.
Or is it a moot point in all ground types of hard rock tailings due to no electrical conductivity in hard rock tailings because they are busted up? I think quartz tailings can be very benign almost to the point of an inability to GB on them.

I reckon if a guy knows the detector he's using at that heap, regardless of type, and can understand that units specific responses to minerals against true target hints, and busted up ground remaining more benign than not, then yeah, I reckon it's a moot point far more often than not.


4.
In regard to depth on tailings between PI/VLF being basically equal, is that true in all instances except for say a GPX or GPZ due to the battery power enabling a much higher level of gain? Like VLF = TDI but VLF < GPX?

I've never used a Good VLF running for that purpose using 4, 6 or 8 aa's that's ever fallen short of a GPX or ZED's so called 'battery power' higher gain level on tailings.
Until a large Mono coil comes into play on the earlier sd/gp and gpx's. That's the only instance I've noticed an advantage.
Exception being the heaps that are entirely made up of small very heavily mineralized shale types that units like the SDC do not like at all. Some of the good vlf's may handle that heap better and deeper than it. On those heaps the PI's can be set up to handle much better than the SDC's shallow timing.
So, while it's not true in all instances, I think it's true in the main.

Having a choice on detectors for tailings that upset some units, is where the real advantage for everyone is.


 

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Good Post argyle, I must admit I run a large 12" Concentric On my VLF most of the time and it will blow the doors off a PI, But hey a PI is not meant for that type of ground so it's not a fair comparison, and I also have a 15" concentric for the VLF too, Now that is a beast, on beer can sized items, 3 to 4 feet  and a 1.3 ozt flat lump of lead is about 28 " to about 35 ",

That's a very interesting post of yours, Having a High Gain VLF Is a great comfort under those condition you describe, I even used it in a fire pit once and I found a heap of coins but all the soil apart from all the burnt ash and charcoal the soil had turned quite Red from the heat, but because it can handle many types of ground and because how the gain works I am stuck at a point where very little impresses me and I can't find another machine that gives me a clear edge in all modes, and my 48khz machine is a wild card on fine bits and since I got that Longscan coil it is a totally different beast In how it picks up real tiny stuff way better than the Twin D coil and another strange effect is that it also lowers  my GB setting by about 20% which means I have a bit in reserve for when I hit the hotter Ground,

John

 

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