Excellent forum - now can a beginner get some VLF gold detecting help please!

[GelatiMiner]

Hi all, I'm a newbie from Australia and first time poster, I have done a lot of reading of this excellent resource and it's been truly invaluable. It helped me to choose my first gold detector - a Fisher Gold Bug Pro which I love!

Recently I spent a long weekend gold detecting around the Victorian Daylesford area which is old gold rush territory. Was hoping (ok expecting!) to find at least a sliver of gold but alas no luck. My father in law is new to detecting too and he had no luck either.

Even though we didn't find anything, it gave me ample time to begin to learn my detector and to start to question myself and my detector and what exactly I was doing. With no experience and bushcraft skills it all felt very random and whilst massively enjoyable I felt a bit lost at times to be honest. I feel I completely understand my device thanks to the excellent manual and resources such as this forum. Where I am lacking is knowing WHERE to detect. What areas are going to maximise my chances?

Here are some of the questions I was hoping some of you gurus could help with:

My Fisher Gold Bug Pro settings for pretty much the entire expedition were gain at 11 o'clock, threshold at either 11 or 12 o'clock, as per the legendary poster and Gold Bug Pro expert, Trinity AU. I liked to detect with a small constant audio tone. I was very careful to ground balance using Ground Grab often.

1. What happens to the ground phase when gold is present? Increases or decreases?

2. In hot ground should I ground balance to hot rocks?

3. What features should be detected first?
- ie old dried up creeks
- bush areas near mine shafts?
- compacted areas of soil full of rocks in places like pine forests?
- areas with lots of quartz sitting on the ground?
- areas with lots of hot rocks sitting on the ground?
- areas with highly magnetised rocks and soil?
- areas next to tree trunks?
- areas with high iron oxide readings on my detector?

4. If I am fully ground balanced, I often get a lot of subtle VCO audio cues - with no target ID in All metal or discriminated mode. Should I investigate these? In some areas I was in I would get this literally every metre or so, became ridiculous quickly.

5. If I investigate 4. and find that after taking a few inches of topsoil off I still can't get a target ID in all metal or discrimination mode, should I abandon the dig and just put it down to a particularly hot patch of soil?

6. If I do get some target id's in discrim mode, but they are weird numbers like 1 or 80 and moving around everywhere should I investigate or is this again just a hot patch of soil?

7. If target appears to move around - ie target id and VCO seem to trigger in different locations with each sweep of the detector is this a hot patch and should it be abandoned?

8. How do I know what bedrock is and do I need to find it to get gold?

9. This is the ultimate question, at what point does an audio signal and ground phase alteration warrant further investigation? I did not know what this threshold was so I had to investigate everything which was time consuming and ultimately did not turn up any gold.


Thanks for your help!
GelatiMiner

GelatiMiner's mining adventures

 

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[Hoser John]

You need a OZ forum as your country is a REAL bugger to detect-look up tinpan on this forum as he walks the walk in OZ everyday and has posted some righteous finds. Forget presets as every area totally different and requirements to run vary unbelieveably. You must regb constantly and a tough place to vlf detect-John

 

[nuggy]

Hi Gelatiminer, All of what John says above, plus see if you can hook up with a club - there are a few in Victoria, I started my detecting there many years ago. Hooking up with someone experienced is about the best thing you could do to speed progress toward finding gold with your detector.
1. Sorry no idea, I just ground balance and dig up most everything.
2. No
3. All of these can be ok, but I like hillsides with bedrock peeking out in places.
4. Audio tones are important to deciding what to investigate further. The tiniest sound change could be a piece of gold, repetition experience is a big help with this, VLF detectors are not the best choice for noisey ground.
5. If you dig down a little, or scrape away the top few inches of soil, the signal should improve if it is gold.
6. That's where experience - repetition will help a little. I don't gold hunt in disc mode, use audio tones to decide what to dig based on experience ( if the last ten of that exact sound were nothing then move on). If the tone is slightly different then dig it.
7. I think this is ground noise, as your soil is so mineralised and that's the price you pay for using VLF in Aussie.
8. Bushcraft and basic knowledge like this is what you need to pick up asap, read some geology, join that club. get on youtube and type in gold bedrock and watch some videos.
9. Even the tiniest alteration could mean a piece of gold - so getting your machine to run quietly and as stable as possible is helpful. The minelab GPX machines are the way to go in Aussie, VLF can be done but it's hard hard hard. There is a VLF machine made by Jack Lange ( I think) that handles ground minerals well, I read up on them a while back, and they really seem to go well.

All the best with it, Nuggy

 

[Jim Hemmingway]

Hello GelatiMiner and welcome to the forum. I'm a silver hunter but below are some of the ideas and techniques that I use to successfully find silver on a consistent basis every prospecting season. I don't know how well they will apply to you in your gold application but nonetheless we'll present them here and you can decide for yourself. And we'll try to address your questions...

(1) Ground phase becomes more conductive… lower numbers on my units’ GB scales…
when ground balance is set over metals and particularly so over rusty iron. The same applies to positive hotrocks. More on this below…

(2) (9) There are some options available to searching hotrock abundant areas with a VLF gold prospecting-capable unit. They work for me, although using the GRAB feature is open to some interpretation. Try these ideas and learn what your unit can do for you. So let’s talk about it…

Non-conductive iron mineralized hot rocks present themselves with one of two distinct responses to a metal detector. They will either respond with a positive target response, or a negative “boing” sound due to autotune threshold “overshoot” reaction to a “negative” hot rock. A positive hot rock will have a ground balance compensation point below our operating GB setting, whereas the negative hot rock will have a ground balance compensation point above our operating GB setting.

The negative hotrock “boing” signal directly results from using an all-metal autotune mode. The autotune initially goes quiet over the rock but struggles to recapture its threshold level as the coil sweeps past the rock. In doing so, it “overshoots” the threshold level briefly and yields an audio response. Thus, as the coil is swept over a “cold” / “negative” hotrock we get the familiar “boing” signal. By contrast, when using a true non-motion all-metal mode, negative hotrocks passed across the coil will simply cause the detector threshold response to go quiet. Magnetite within a rock structure is normally responsible for negative hot rock responses. These are fairly easy to recognize and can be ignored.

Positive hotrock signals can be frustrating to electronic prospectors because their signals sometimes mimic nugget signals. Many locate in the upper portion of the target ID iron range, as do many small nuggets concealed in highly mineralized ground. Fortunately, hotrocks that respond to metal detectors tend to reside very close to or on the surface. Maghemite is often the culprit responsible for positive hot rock responses.

Positive non-conductive hotrocks can sometimes be distinguished from good targets because they lose their signal more quickly than precious metal targets of similar size as the coil is raised above the ground. But this is variable to the type, size and magnetic strength of a given hotrock and I prefer not to use this method as a definitive yardstick. With experience you’ll learn to visually identify most hotrocks in your area, and most are on the surface in plain sight.

Some amount of iron discrimination, to be determined in the field for the type of hotrocks that are encountered, will eliminate these pests. The more persistent ones will sometimes require discrimination settings slightly above the level needed to eliminate small bits and pieces of metallic iron. However, this level of discrimination will also eliminate some small nuggets that fall into a similar conductive range. I think it a worthwhile tradeoff to search very trashy areas or areas proliferate with positive hotrocks using a suitable level of discrimination. At least you can hunt such an area with a VLF unit… and electronic prospecting is supposed to be fun and not a futile exercise in frustration.

Some operators prefer to ground balance to an area’s prevalent positive hot rock type and search at that GB setting. But this technique will leave you improperly ground balanced below that required for the surrounding terrain… such that depth / sens will be reduced… and this sens reduction will be directly related to the amount of ground balance offset and the harshness (strength) of the magnetic susceptible ground minerals. Reducing sensitivity helps with mild hotrock / ground anomaly signals but only to the extent that sens reduction doesn’t eliminate the prevalent gold size in the search area beyond what is acceptable to you.

In conjunction with the above comments, you should practice ground balancing at the elevation above the terrain that you will swing the coil. It is important to maintain that coil elevation, and more so over tough ground minerals, to avoid precipitating ground mineral responses. Try the above ideas and compare your settings over a test nugget buried at a reasonable depth and see what the search conditions will allow you to do… it is well-spent time.

Where hotrocks are not overwhelming, I prefer to use the “GROUNDGRAB” or sometimes called the “GRAB” feature available on many of the modern prospecting-capable detectors to assist with target signal evaluation. The FASTGRAB feature makes searching hotrock areas properly ground-balanced in the all-metal motion mode more feasible because it takes only a moment to check out a suspect hotrock signal and then quickly re-balance to the ground and continue searching. I do not swing the coil back and forth over the target signal while enabling the GRAB feature, but rather I pump the coil exactly over a target signal just the same as if you are ground-balancing over clean ground… four or five pumps max. Swinging the coil may tune-out metallic targets and that result voids this technique. Normally small silver here does not lose more than one or two GB digits towards the conductive (lower numbers on my units’ GB scale) end of the GB scale and any size silver from sub-grain and upwards retains its signal in all but extreme ground mineral conditions. So to reiterate the answer to your question, yes… ground phase becomes more conductive when set over metal targets (especially rusty iron) and positive hotrocks.

For example, our positive diabase hotrocks that produce good strong signals will read consistently in the upper iron range at target ID “14” on the F75. But when ground-balanced using the GROUNDGRAB technique they lose their positive signal, their target ID disappears, and there is always a small reduction in the ground balance readout. Other positive non-conductive iron-mineralized hotrock types in this area react similarly but experience more variable GB reductions. GB reductions over non-conductive positive hotrocks depend entirely on a given rock’s ground (phase) balance compensation point. I suggest you try this technique and see how it works for you… but for meaningful results… ensure the metal targets are buried and not simply placed on the ground’s surface.

So as a final comment on this subject, we use some judgement according to hotrock prevalence. In hotrock abundant areas where the gold / silver is sufficiently large to respond, a suitable PI unit may / will be a better choice.

(3) I agree with Nuggy that all such areas can produce, but I prefer hillslopes for metal detecting silver float here… easier digging…whereas hillslopes in gold areas are much less likely to have been worked due to a lack of readily available water. Also look above and alongside stream channels.

(4) This is a tough question without being there to see and hear responses. If you’re operating properly and keeping the coil uniformly at ground balance elevation, with your gain under control such that it is suitable for that ground… then you have to evaluate repeatable signals. Ground anomalies will come with experience as nuggets normally yield a good “zip zip” type of signal. But sometimes small red-hot maghemite positive hotrocks also yield a very similar signal. Evaluate these or operate as described above.

(5) (6) Just as Nuggy says. Look… pay no attention at all to target ID on anything but the most shallow and strong signals. Always scrape away some material and recheck. If the signal increases and you feel that it could possibly be gold, then dig it if in any doubt.

Target ID in moderate to harsh mineral conditions is not reliable at any real depth. Most smaller silver in my area reads as iron. If you want to be thorough you must remove some material and re-evaluate the signal. Or just resign yourself to digging such targets and enjoy the great outdoors while you’re at it. Remember… electronic prospecting isn’t easy… and the only sure target ID / discrimination is your pick magnet / and digging tool.

(7) Could be ground anomalies or could be rusty iron. Iron… even small but elongated iron exhibits both conductive and magnetic properties… hence the signal oftentimes seems to “move around”.

(8) As Nuggy says but I also recommend you read Dave Johnson’s excellent booklet entitled “Gold Prospecting with a VLF Metal Detector” at the following link…
http://www.fisherlab.com/hobby/davejohnson/Dave'sGoldbook-reders.pdf

Bedrock refers to the solid unweathered rock underlying surface substrates / soils. In a prospecting context it also can refer to false bedrock such as cemented gravels… caliche…normally a hardened layer of sand / gravel cemented together over time by precipitated calcium carbonate. These trap placer gold… and certainly improve your chances. Gravity pulls heavy gold downwards until such formations stop it.

(9) Discussed above, but initially keep it simple… learn the basics with your unit and don’t be too concerned with ground phase changes generally. Look for and become familiar with the sharp distinct nugget signals as compared to anomalous ground signals and many hotrocks. Good luck, enjoy the detecting…be persistent… and exercise patience.

Jim.

 

[Ausgoldhunter]

1. What happens to the ground phase when gold is present? Increases or decreases?

A: answered above


2. In hot ground should I ground balance to hot rocks?

(Balance over hot rocks IF you believe it may actually be a good signal)

3. What features should be detected first?
- ie old dried up creeks (Yes, if they are in gold baring areas, target inside bends of these creeks, but don't limit yourself to them cover it all)
- bush areas near mine shafts? (Always a good idea, tailing piles are worth hitting, i detect over them, then with my steel rake, i scratch away the surface 1 or 2 inches, and go over it again)
- compacted areas of soil full of rocks in places like pine forests? (Doesn't hurt to try, but keep in mind, gold is heavy, given enough time it will sink deep)
- areas with lots of quartz sitting on the ground? (Quartz is a host of gold, but not always)
- areas with lots of hot rocks sitting on the ground? (This is what some of us call *HOT ROCK HELL* south east NSW frikn iron stone!)
- areas with highly magnetised rocks and soil? (Never really thought about it)
- areas next to tree trunks? (well worth checking, I pulled half a gram out of the root ball of a fallen tree last year)
- areas with high iron oxide readings on my detector? (Again, if you know it to be a gold baring area, they sure, maybe)

4. If I am fully ground balanced, I often get a lot of subtle VCO audio cues - with no target ID in All metal or discriminated mode. Should I investigate these? In some areas I was in I would get this literally every metre or so, became ridiculous quickly.
(Yes, usually a quick boot scratch over the surface will give you hints on the next swing.. ie, did it get louder? or vanish.. in either case its dig or no dig)

5. If I investigate 4. and find that after taking a few inches of topsoil off I still can't get a target ID in all metal or discrimination mode, should I abandon the dig and just put it down to a particularly hot patch of soil?
(No. I feel like you're focused on that meter a little too much, Just because a target doesn't read, doesn't mean it doesn't exist, yes it could be mineralization, or a hot rock, could also be a nice 1g nugget)

6. If I do get some target id's in discrim mode, but they are weird numbers like 1 or 80 and moving around everywhere should I investigate or is this again just a hot patch of soil?
(Mineralization, pain in the VLF ass)

7. If target appears to move around - ie target id and VCO seem to trigger in different locations with each sweep of the detector is this a hot patch and should it be abandoned?
(very small target being swept around, or again Mineralization) eing swept around, or again Mineralization) [/B]

8. How do I know what bedrock is and do I need to find it to get gold?
(No. I've found quarter to half gram nuggets less than 2cm deep, but if you're hunting creek beds that's generally where the golds going to lay)

9. This is the ultimate question, at what point does an audio signal and ground phase alteration warrant further investigation? I did not know what this threshold was so I had to investigate everything which was time consuming and ultimately did not turn up any gold.

(Ignore the meter unless its a really hot signal, I've found nuggets .09 and .1 gram 2" deep that only made the threshold on my detector change slightly, remember its VLF the gold you're going after is not going to scream at you all that often
1 and 2 Grain nuggets might only give you a tiny rise or dip in threshold, which is why most of us recommend a good set of headphones) I believe i paid $49 for mine and they are pretty much amazing.. they are powered, with audio amplifier built in.. sadly not sold anymore...

Anyway hope some of this info is helpful.

 

[Alex Burke]

Wow that was informative thanks to both of you for asking and answering. I found some really good info a couple of months ago when I was thinking of going to Vic. It was on the 4umer site some guys there have compiled mineral map overlays and great discussions of diff areas. I bookmarked some I think not at my comp at moment tho. G'Day mates
http://books.google.com.au/books/re...rintsec=frontcover&output=reader&pg=GBS.PA101

 

[Ausgoldhunter]

Oh and also Minelab PI... GP, GPX, etc...

 

[GelatiMiner]

Thanks all - I knew you guys would be able to help me and I hope to one day get good enough at the black art that is gold detecting that I too can give back a wealth of knowledge to the forum to help someone who is perhaps starting out like me.

Jim: thanks for the fantastic detailed reply!

In reply to your reply:

1). Thanks - so I need to commit to memory - conducive items (ie positive hot rocks or Iron scrap) have a negative effect on ground phase - got it.

2). Great explanation on sounds. Certainly I don't recall the "boing" sound in my expedition, nor do I recall my detector going quiet on certain rocks - so I can ascertain I didn't encounter any negative hot rocks.

When you mentioned that positive hot rocks are usually closer to the surface that sounds bang on...and boy are they magnetic!
Ok so my line of defense against these guys is to possibly raise the coil and check the drop off in audio - I am ordering a small gold nugget off ebay I plan to use to help test with and I can practice the same thing with that and the hot rock I bought home to judge the difference.
Also good to know I can use some discrimination but yes the lack of depth and sensitivity as a result always worrys me!
Your point about ground elevation fascinates me. I wouldn't be surprised if in the process of trying to investigate a weak signal I put the coil closer to the ground or possibly on it - this is probably a classical rookie mistake.
Where you say that you like to GROUNDGRAB to quickly check a suspect hotrock -would I be correct in saying that is to listen whether the positive audio cue disappears and if so it's not gold? If it is gold and you GROUNDGRAB to that would you still get the zip zip positive response? This sounds like an invaluable way to quickly check a 50/50 target.

3). Thanks

4). Sounds like the gold signal should be decent and I can use the technique above to cancel out the hotrocks

5). 6) - Yes as another poster said I may have been relying too much on the target ID. I'll continue to dig the targets that have a reasonable audio cue regardless of target ID.

7). Yes some were Iron targets such as nails, or long lines of small grain like positive hot rocks which seemed to throw the unit around a bit. Other times it just appeared to be the soil - however I did not have a magnet on my pick, my father in law did and sometimes he was too far away for me to grab his magnet. So that's something else i've gotta get - a magnet!

8). that PDF looks sensational, will absorb it. As for bedrock I suppose there is no way to be 100% sure you are at bedrock level unless you have some kind of geo-phys information .

9). I am getting a small nugget off ebay to use for testing, I should be able to create a pretty decent test bed with the hot rocks I brought back from my expedition.


John - I would join a club however I can only get away from the city to detect ever 3 months or so so not sure it would be worthwhile, but certainly I take your point.

Nuggy- thanks I get your point about repetition, the "ghost" positive responses that seemed to just be hot soil seemed to be very similar and by the end I was disregarding some however I was constantly grappling with myself as to whether I had just left a nugget behind! Hopefully getting a test nugget will help a bit.
Regarding the tiny audio alterations potentially being gold I guess this is an experience thing and also a hearing thing. I have cheapy headphones that came with the detector but to be honest was too scared to use them in case I stood on a snake or something - I suppose your eyes are more invaluable in that regard than ears, but still I like my full faculties when in deep grass in forest.

AusGoldHunter - Excellent, you confirm what Jim above said, that it's worth balancing to a hot rock to check a target. This is because the gold should still trigger I would imagine.
I take your point about the target ID and will learn to treat it less like the source of truth. Great advice on where to look.

Going hunting again in a couple of months, possibly to the Bendigo Victoria region where I can put some of you guys advice to the test and will be sure to report back!

Cheers,
GelatiMiner


GelatiMiner's mining adventures

 

[Steve Herschbach]

You guys are to be commended for your detailed responses to the original post. Good job!