Minelab Equinox 900 Or Manticore For Prospecting

[jasong]

1 hour ago, GB_Amateur said:

I understand the first two sentences, but am confused on the last sentence.  (I'm sure those familiar with the type of areas you refer aren't confused....)  Could you go a bit further in explaining this?  Just to emphasize my ignorance, I wasn't aware that lode gold and placer gold can be present in the same location -- vertically separated.  Also the part about "heavy mineral concentrates (being) formed..."  I can guess/surmise what this means as it seems self-explanatory but I can also think of other interpretations.  (All or this may be in Chris Ralph's book, so maybe time for me to reread.  Not having been trained in geology nor having a lot of experience searching for native gold, I've missed a lot on first and even second reading.)

Sure, I can explain further. Technically (and legally) speaking, the instant a piece of gold becomes separated from it's in-situ source - it's placer. So they definitely can exist in the same location because placer gold in general is just detritus that eroded from a lode source at some point further up. The second it separates from it's vein it's placer, even if it's only 1mm from the source at that point. When I talk about detecting lode gold areas, I'm talking about detecting both placer and lode gold in the sense that usually first you find a gold line, or sometimes a more widely scattered occurence of detrital gold (placer), eroding down a hillside. This often leads to nothing since the source pod/vein is long eroded away, but sometimes it leads to pockets of gold (lode) still existing. So in a sense, pocket gold hunting starts with looking for placer leads in a lode source area.

To understand heavy mineral concentration, it's a matter of statistics and physics. On that hillside you have only the minerals derived directly from that hillside, and (generally) only from that specific slope of the hill. However, if you walk down to the wash at the bottom which drains that hillslope, you are now dealing with minerals from every hillslope that wash drains. It's usually more likely that this wash will be "hotter" than the hillside as a result. The more source material, the more heavy minerals available to concentrate. That's the statistics part in action - increase your source material abundance, increase your potential heavy mineral concentrates. 

Now: as you exit the lode area and everything is now just 100% placer, and the lode material contribution to the gravel decreases as more different gravel sources are introduced and intermixed, you may actually get less heavy concentrates as you go downstream. But I'm talking about detecting lode source areas where the gravels are all locally derived and similar, not far downstream in placer areas. So it's an important distinction to understand.

The exception to all this of course being where the hillslope itself is composed largely of localized hot rocks like volcanics, serps, etc and thus is already "really hot" irregardless of soil concentration. But what I was referring to is mineral concentrates, not country rock hotness. I'm talking in generalities because there are a hundred exceptions where conditions are specific to one location and not another.

Anyways, think of a gold pan after you've applied energy to the system (aka "panned" the material) - the closer to the bottom you get, the more heavy minerals there are. That's the physics/gravity part in action. And just like further up in the pan the heavies are less and less concentrated, further up the hill there has been less material concentrated, and less overall energy put into concentration/ordering. In this case, the energy being applied to the system is wind and gravity though, not a person panning. Well, maybe it's more like panning where a slow, constant source of new material is always added to the top and the person is panning glacially slow (representing natural erosion/eluvial processes)...but you get the idea. 

Now, when you get down into the washes themselves, you also have the energy from water adding to the concentration action (this is where often those annoying, near impossible to detect, magnetite layers get formed), plus a ton more material from surrounding hillsides. And that's why often the washes are hotter than the hillslopes with little local patches eroding down them. 

Again, speaking in broad generalities here. There are thousands of exceptions and certainly everyone can give an example of "well, this one time..." or "that's not how it is here". But I'd have to write a book to cover all the exceptions and why specifically they are different. 

[GB_Amateur]

Great detailed but clear explanation, Jason.  Thank you for taking the time to write that up.  My main cause of confusion was thinking 'placer' and 'alluvial' are the same.  Also, thanks for pointing out that there are many exceptions to your general description.  Often people leave that out leading to much disagreement/confusion. 

[WesD]

Another technical word that gets thrown around is elluvial .

Example- Nuggets found close to their vein source are usually jagged and angular, and are categorized as elluvial gold, or an elluvial placer

[jasong]

2 hours ago, GB_Amateur said:

Great detailed but clear explanation, Jason.  Thank you for taking the time to write that up.  My main cause of confusion was thinking 'placer' and 'alluvial' are the same.  Also, thanks for pointing out that there are many exceptions to your general description.  Often people leave that out leading to much disagreement/confusion. 

Placer and alluvial pretty much are the same, in the respect that they both indicate derivational material that came from somewhere else and was deposited via some mechanism. It's just that it doesn't matter if it's 1mm or 1 mile. Placer is a more broad term, alluvial is a more specific term. In a venn diagram, placer would contain all alluvial deposits, but alluvial wouldn't encompass all placer deposits.

As WesD notes, eluvial is another similar term. It's generally used in prospecting to refer to material eroding via wind and gravity rather than water. This doesn't tend to transport the erosional products as far as alluvial processes do.

An example of real world eluvial deposits that get posted here occasionally would be pocket gold in SW OR/NV/CA, many of the huge gold bearing pediments in NNV (themselves often derived from pockets), or places like the large nugget bearing flats and pediments in Quartzsite and Gold Basin.

Examples of posted alluvial deposits would be the famous gold bearing rivers in California as the most obvious one. But also, I would personally classify the paleoplacers (ancient riverbeds) as alluvial as well. Also things like beach placers (Oregon, AK, CA to some extent). And dry washes like in the deserts in AZ.

The two can intermix also. An old stranded bench deposit high up in a mountain which has been exposed by erosion and started to erode downhill via gravity is what I would classify as a secondary eluvial deposit - it's source being alluvial - and the alluvium's source being ultimately lode from either alluvial or eluvial erosion.

Eluvial and alluvial deposits can be anything - not just gold. Including heavy mineral concentrates, zircon, uranium, diamonds, or even just random detritus. Uranium deposits are interesting because they are usually filed as placer claims even if they are in hard rock, but the reason is beyond the scope of this post.

Anways, I don't want to side track the thread anymore so I'll stop there. 

[blackjack]

On 12/5/2022 at 11:23 AM, Gold Catcher said:

I think the two (main) reasons why VLFs have done so well in the past are that (1) there was no PI technology around for comparison and (2) a lot more easy gold was still in the ground. Now, it's getting much more difficult to recover gold, a fact that requires some good depth performance in addition. With 50% more power output the Manticore holds promise in this aspect, hence this would be my choice over the Nox (if I had to choose a VLF....). I personally would use it mostly with a small coil though. But then again, why not the Axiom? 

GC

P.I. machines have been around since 1995, to my knowledge. The latest generation of VLF's are just as sensitive on small gold, more sensitive than older generation P.I.'s from what others say,  and have their place in shallow ground as well as having far better discrimination. In the perfect world a P.I. machine as well as a VLF would be what you need, there are times when a VLF can be used. But we don't live in a perfect world, well at least I don't and there's one factor no one on this forum seems to consider, cost. The cheapest P.I. machine I would consider is the SDC2300 if my budget allowed, but at $4,500 au I can't justify the cost, maybe if I lived on a gold field. A quick glance at my gear will tell you that I use a nox 800 $1050 au on special last winter. It does handle mineralized ground pretty well for a VLF, at least the ground I've used it on, Western Australia and here in Tasmania were some ground has so many hot hotrocks that you need to notch discriminate, 11- 16 or some variations of that range, so it's versatile. For those of us on a budget it's the only way we can get out and nugget shoot. Please correct me if I'm wrong Gold Catcher but it seems your only VLF is a GM 1000, a great switch and go machine, based on what others have said, but you could do better in my opinion which may have you look at VLF's differently. I don't want to start a debate P.I.'s vs VLF's for gold hunting, in clean, mineralized ground we all know the answer. 

[Gold Catcher]

16 hours ago, blackjack said:

Gold Catcher but it seems your only VLF is a GM 1000, a great switch and go machine, based on what others have said, but you could do better in my opinion which may have you look at VLF's differently.

I have been using the GM and the GB2, with good success. Both excellent machines for their purpose without a doubt. The newer gen ML VLFs are fantastic choices with many options for successful hunting. But a VLF will always remain a VLF, with the principle caveats (and benfits) of this technology remaining. For my particular needs a PI or ZVT are the much better choices, at least for the most part. But in general diversity is key. Not one detector, or one tech, will fit all needs. But of course, this is also a budget question, as you are pointing out. I hope this helps.

GC

[glacialgold]

On 12/4/2022 at 1:58 PM, phrunt said:

I like VLF's for gold, they will find gold the other detectors will not, generally very small gold and it sure won't pay the bills but for someone that does it for fun they're great and for pure bedrock detecting they're hard to bea

Great point, and that's 100% my circumstance.

There aren't any big gold deposits where I'm located, but I do have convenient access to creeks (right on bedrock at the trough) and those creeks source from the glacially-deposited gold-bearing material existing in this part of Indiana. After the floods recede each spring, I see old-timers on the same creeks I work scraping out those tiny crevices. I've personally found a few chunky flakes and pickers (which is like <0.05g to 0.1g from my perspective) panning, and they ring up just fine on the 800 and Legend in 2-3" air tests. Ground here isn't all that hot, and actually hot rocks are a significant indicator of a zone of interesting glacially-deposited source material.

No expert here by any means, but I'm using (aka, playing around with) my VLF machines to hopefully find a target,  but more so a good zone overall. I'd be over the moon if the target turned out to be an actual picker. More likely, however, is it's a place where I'm going to collect gravel to pan or sluice later.  I've no use for a PI, as a result...but I'd love to play around on one those machines, regardless!

My two cents, so feel free to take it with a grain of whatever. 🙂

[glacialgold]

On 12/5/2022 at 12:22 PM, jasong said:

Sure, I can explain further. Technically (and legally) speaking, the instant a piece of gold becomes separated from it's in-situ source - it's placer. So they definitely can exist in the same location because placer gold in general is just detritus that eroded from a lode source at some point further up. The second it separates from it's vein it's placer, even if it's only 1mm from the source at that point. When I talk about detecting lode gold areas, I'm talking about detecting both placer and lode gold in the sense that usually first you find a gold line, or sometimes a more widely scattered occurence of detrital gold (placer), eroding down a hillside. This often leads to nothing since the source pod/vein is long eroded away, but sometimes it leads to pockets of gold (lode) still existing. So in a sense, pocket gold hunting starts with looking for placer leads in a lode source area.

To understand heavy mineral concentration, it's a matter of statistics and physics. On that hillside you have only the minerals derived directly from that hillside, and (generally) only from that specific slope of the hill. However, if you walk down to the wash at the bottom which drains that hillslope, you are now dealing with minerals from every hillslope that wash drains. It's usually more likely that this wash will be "hotter" than the hillside as a result. The more source material, the more heavy minerals available to concentrate. That's the statistics part in action - increase your source material abundance, increase your potential heavy mineral concentrates. 

Now: as you exit the lode area and everything is now just 100% placer, and the lode material contribution to the gravel decreases as more different gravel sources are introduced and intermixed, you may actually get less heavy concentrates as you go downstream. But I'm talking about detecting lode source areas where the gravels are all locally derived and similar, not far downstream in placer areas. So it's an important distinction to understand.

The exception to all this of course being where the hillslope itself is composed largely of localized hot rocks like volcanics, serps, etc and thus is already "really hot" irregardless of soil concentration. But what I was referring to is mineral concentrates, not country rock hotness. I'm talking in generalities because there are a hundred exceptions where conditions are specific to one location and not another.

Anyways, think of a gold pan after you've applied energy to the system (aka "panned" the material) - the closer to the bottom you get, the more heavy minerals there are. That's the physics/gravity part in action. And just like further up in the pan the heavies are less and less concentrated, further up the hill there has been less material concentrated, and less overall energy put into concentration/ordering. In this case, the energy being applied to the system is wind and gravity though, not a person panning. Well, maybe it's more like panning where a slow, constant source of new material is always added to the top and the person is panning glacially slow (representing natural erosion/eluvial processes)...but you get the idea. 

Now, when you get down into the washes themselves, you also have the energy from water adding to the concentration action (this is where often those annoying, near impossible to detect, magnetite layers get formed), plus a ton more material from surrounding hillsides. And that's why often the washes are hotter than the hillslopes with little local patches eroding down them. 

Again, speaking in broad generalities here. There are thousands of exceptions and certainly everyone can give an example of "well, this one time..." or "that's not how it is here". But I'd have to write a book to cover all the exceptions and why specifically they are different. 

Anyone new to prospecting should read this post, read it again....and again as necessary....and be able to recite it from memory. Stellar.

[rled2005]

Equinox 900 manual:

4901-0419-2 Inst Manual, EQUINOX 700 900 EN.pdf (minelab.com)

[MSC]

Gerry, you should have been born with a bigger mouth, nice gold.