Detecting bigger gold in NSW...."Alluvial" vs "Eluvial"

[Gold1hunter]

Thanks Moneybox...the thing with nuggets is once you take one away from its hiding place they don't replace themselves. It is still out there mainly because our goldfields are huge and it would take a lot of detecting to get even a small proportion of the gold nuggets still on offer. Hope some have your name on them mate.

If you had 1 square km to grid @ 50cm wide lines you would have to walk 2,000km to complete it & really you should do it again to box it to be sure you didn't miss any. After a hard full day of walking/detecting most wouldn't even have covered an area as big as their back garden.

 

[WalnLiz]

If you had 1 square km to grid @ 50cm wide lines you would have to walk 2,000km to complete it & really you should do it again to box it to be sure you didn't miss any. After a hard full day of walking/detecting most wouldn't even have covered an area as big as their back garden.

Exactly right Goldhunter...and in WA alone the goldfields cover thousands of square kilometres. On our NSW fields if you combined every prospector with a metal detector it would take 100 years to cover just the creeks alone within the fields. I've been detecting for close to 50 years and more seriously ever since the old Garretts first came out and would say that I haven't covered more than 100 creeks, where I could say those creeks are worked out. The GT in VIC is also so huge that gold will always be there for our kids and grand kids.

 

[user 4386]

Which is why it is important to focus on the most likely areas (as WalnLiz have pointed out with their discussion of eluvial gold when chasing coarse and nuggety gold)

It is the same when chasing alluvial gold. I looked at this in detail, and while gold can transport tens of km down a creek, all but the first couple of km from the source is usually finer than you would want. In fact we looked at one large goldfield in particular where there were good records (Ballarat) and most nuggety gold was in gullies only 300 m or less from the source. Nuggets over 15 kg (of which Ballarat had a number) in a number of cases never even made it to a gully but were found on hillslopes below the source reefs - all only got as far as small gullies immediately below the reefs - they were not transported long distances along the lead streams (which had lots of gold, but finer).

I have sometimes had comments when I have posted that it was "academic" and that "gold is where you find it". Neither is so - some simple knowledge of geology increases your chances by 1000% or more, and coarse gold only occurs in specific locations, to some degree predictable.

(1) In rocks of specific type (although these will differ a bit on different goldfields locations).
(2) In structural zones, commonly narrow and linear within those rock types
(3) nuggety almost on top of the source reefs (and their structural projections) or downslope of them
(4) nuggety in gullies and streams within no more than 500 m in the main from the source reefs, and even in those cases where they are not covered by alluvial brought downstream from elsewhere

Here is the diagram that I prepared for nuggets over 15 kg (all mine shafts shown are those on quartz reefs, not alluvial, thus giving the position of source areas). I did another one for coarse gold and smaller nuggets in streams (and old buried leads), which gave the 300-500 m transport distance, which if you look at the scale of this map of the goldfield is a tiny proportion of the goldfield area. Imagine how much you reduce the area that is worth focussing on if you limited yourself to within those parameters.

 

[user 4386]

If you look at the shafts you will see that there are three roughly parallel mineralized reef zones, each about 16 km in length, Ballarat West, Ballarat East and Little Bendigo. Something that is not obvious if you are just wandering around with no control. The GSV mineral localities layer can be separated by those with any GIS expertise into alluvial and hard-rock gold shafts (i.e. separate attributes) so that you can define source areas for all Victorian goldfields, not just Ballarat. You can then call up the stream layer and superimpose it on the hard-rock shafts, and sketch in the boundaries of the areas worth detecting.

In some cases there is also a lead layer, and some of the buried leads can have a vastly different course to modern streams and even be cut by them, Where such a layer exists it can also be superimposed, as these can become gold source areas for modern streams where cut by them. You can also call up rock type layers (avoid granite in most of central Victoria, avoid Tertiary basalt flow, avoid areas of young alluvium far from the edge of hills, focus on Devonian or older rocks in Victoria for gold). Superimpose them all as on this map.

The reason hard-rock shafts occur over a greater width in some areas is because in detail there are really two mineralized zones close together at Little Bendigo (Nerrina) and three at Ballarat West. So if you zero in to a larger scale on the areas you choose, you can see these zones start to separate into separate linear zones and focus your efforts even more.

 

[WalnLiz]

Which is why it is important to focus on the most likely areas (as WalnLiz have pointed out with their discussion of eluvial gold when chasing coarse and nuggety gold)

It is the same when chasing alluvial gold. I looked at this in detail, and while gold can transport tens of km down a creek, all but the first couple of km from the source is usually finer than you would want. In fact we looked at one large goldfield in particular where there were good records (Ballarat) and most nuggety gold was in gullies only 300 m or less from the source. Nuggets over 15 kg (of which Ballarat had a number) in a number of cases never even made it to a gully but were found on hillslopes below the source reefs - all only got as far as small gullies immediately below the reefs - they were not transported long distances along the lead streams (which had lots of gold, but finer).

I have sometimes had comments when I have posted that it was "academic" and that "gold is where you find it". Neither is so - some simple knowledge of geology increases your chances by 1000% or more, and coarse gold only occurs in specific locations, to some degree predictable.

(1) In rocks of specific type (although these will differ a bit on different goldfields locations).
(2) In structural zones, commonly narrow and linear within those rock types
(3) nuggety almost on top of the source reefs (and their structural projections) or downslope of them
(4) nuggety in gullies and streams within no more than 500 m in the main from the source reefs, and even in those cases where they are not covered by alluvial brought downstream from elsewhere

Here is the diagram that I prepared for nuggets over 15 kg (all mine shafts shown are those on quartz reefs, not alluvial, thus giving the position of source areas). I did another one for coarse gold and smaller nuggets in streams (and old buried leads), which gave the 300-500 m transport distance, which if you look at the scale of this map of the goldfield is a tiny proportion of the goldfield area. Imagine how much you reduce the area that is worth focussing on if you limited yourself to within those parameters.

View attachment 2713

Very good informative info there Goldierocks and the sort of knowledge one needs to be successful when nugget hunting. It's these kind of replies that certainly help answer many of the questions that the newcomers to the hobby appreciate. Cheers Wal.

 

[Davent]

Great post Wal and Liz, cheers.
Amazing gold from NSW.

 

[WalnLiz]

Great post Wal and Liz, cheers.
Amazing gold from NSW.

Hoping that I can get more newcomers keen on research davent...I know that it will get them more gold in the long run.

 

[Gregyem]

If you look at the shafts you will see that there are three roughly parallel mineralized reef zones, each about 16 km in length, Ballarat West, Ballarat East and Little Bendigo. Something that is not obvious if you are just wandering around with no control. The GSV mineral localities layer can be separated by those with any GIS expertise into alluvial and hard-rock gold shafts (i.e. separate attributes) so that you can define source areas for all Victorian goldfields, not just Ballarat. You can then call up the stream layer and superimpose it on the hard-rock shafts, and sketch in the boundaries of the areas worth detecting.

In some cases there is also a lead layer, and some of the buried leads can have a vastly different course to modern streams and even be cut by them, Where such a layer exists it can also be superimposed, as these can become gold source areas for modern streams where cut by them. You can also call up rock type layers (avoid granite in most of central Victoria, avoid Tertiary basalt flow, avoid areas of young alluvium far from the edge of hills, focus on Devonian or older rocks in Victoria for gold). Superimpose them all as on this map.

The reason hard-rock shafts occur over a greater width in some areas is because in detail there are really two mineralized zones close together at Little Bendigo (Nerrina) and three at Ballarat West. So if you zero in to a larger scale on the areas you choose, you can see these zones start to separate into separate linear zones and focus your efforts even more.

That's a tidy piece of investigation. Thanks for the overview of the strategy. Does Min view provide the level of detail to conduct this sort of analysis. I am shortlisting some NSW forestry areas for upcoming ventures with my wife this Spring. I would love to approach it in such a clever way.
Greg

 

[user 4386]

That's a tidy piece of investigation. Thanks for the overview of the strategy. Does Min view provide the level of detail to conduct this sort of analysis. I am shortlisting some NSW forestry areas for upcoming ventures with my wife this Spring. I would love to approach it in such a clever way.
Greg

I have not looked at MinView for years - Victoria is certainly very detailed. It produced a lot more gold (five times as much as NSW in the 19th C than NSW, from a much smaller area). and early mapping was very detailed. Try playing with Minview yourself. Note that in Victoria it is not obvious to the casual user that all this information is there, like separation of alluvial from hard rock mine shafts. I used to be good on GIS, so I would download the mineral localities and mine workings layer file, separate the "gold" deposits attributes column in the file, then separate the alluvial attributes column in my new gold file from the hardrock....

 

[Jaros]

All this echrinuvial etc is making me analuvial!! Get back to basic prospecting- simple english please/

 

[user 4386]

All this echrinuvial etc is making me analuvial!! Get back to basic prospecting- simple english please/

It gives 1st year geology students similar headaches - all those Latin words. But many prospectors here use geological maps, these words appear on those maps, and to the knowing it tells them where to detect and not to detect. Basic prospecting is what you do in the end, but it is so much better done where your chances of success are 1000% better,,,,

I have seen you telling beginners how they should do the desktop groundwork themselves before they go out.

 

[WalnLiz]

It gives 1st year geology students similar headaches - all those Latin words. But many prospectors here use geological maps, these words appear on those maps, and to the knowing it tells them where to detect and not to detect. Basic prospecting is what you do in the end, but it is so much better done where your chances of success are 1000% better,,,,

I have seen you telling beginners how they should do the desktop groundwork themselves before they go out.

All terms that "need" to be known, and its those that take the time to fully understand the terms that can best make sense of geological maps...understanding terminology is part of the necessary learning curve unfortunately...

 

[Gregyem]

I have not looked at MinView for years - Victoria is certainly very detailed. It produced a lot more gold (five times as much as NSW in the 19th C than NSW, from a much smaller area). and early mapping was very detailed. Try playing with Minview yourself. Note that in Victoria it is not obvious to the casual user that all this information is there, like separation of alluvial from hard rock mine shafts. I used to be good on GIS, so I would download the mineral localities and mine workings layer file, separate the "gold" deposits attributes column in the file, then separate the alluvial attributes column in my new gold file from the hardrock....

Hmm those historical stats certainly give some perspective. Thanks. Yeah I used to use Arc map and ESRI Arc GIS a long time ago so have some grasp but I am sure it's advanced a lot since then. I will see what I can do in Min View. Be great if I can create some Boolean expressions to see if I can can get some projects resulting from a number of prerequisite criteria like "State forest And metamorphic contact zone And hard rock mine And Fossicking Zone". It certainly would be helpful.

 

[sam-u-al]

well..... what can I say WalnLiz... the above is astonishingly clear information... I am in coastal Nth NSW, and not really gold country... but am planning on travelling some... so .. I will do my geology research and accessing the Geo Australia maps is also very useful info... I am definitely a Newbie at this... but for the last decades have read a lot about a lot of stuff... Many have gone before us... and I am sure many more will follow... Thanks Wal... take good care

 

[sam-u-al]

Hey Wal... a great video... 6 years ago …

Has the 17 x 13 been superseded by a better coil?

 

[WalnLiz]

Hey Wal... a great video... 6 years ago …

Has the 17 x 13 been superseded by a better coil?

Hasn't been superseded Sam and is still my "go to" coil even today. In places like Tibooburra I prefer the 12" Evo mainly because the gold is generally so small. Almost every where else I prefer the 17x13.

 

[sam-u-al]

Mmm... thanks... I rocked into Tibooburra decades ago two weeks prior to a Rodeo Weekend (exactly two weeks prior to, and camped in the desert to the west of the town in the boulders drawing and dreaming)... and when I came back to town, found no accommodation was available due to the Rodeo Weekend about to happen (unbeknown to me at the time) and thus, was going to sleep under the school when a resident graciously saw my intent and fed me with a meal and a bed... then … …next day I was outside the pub and was drawing the pub in pencil (still hav the drawing somewhere) and the pubs' cold shoulder attitude from the previous day was dropped like a Hot Rock noise because I could draw and paint (to the point of attitude change where I was almost a celebrity... lol..). but then it was about to rain buckets so the whole Rodeo Weekend was cancelled and I became part of that flurry of activity,....as all roads were about to be closed etc... and so, the next day I immediately ended up in Broken Hill via a hitch out in time to miss the flood... The whole place around Tib. is amazing, the colours of the ground, the horses, the people, and in the boulders I camped around, an iron plug stuffed up my trig point triangulation (that was completely haywire), as my compass was 30-40% out, ... so I scratched Star Chart directions on the ground with a stick, and discovered next day how deep the magnetic anomaly is there.. Anyhow... I am sure that you could write a book on your escapades as well... lol... I am about to buy some coils n 2 detectors of some kind... a VHF and a PI... and will do another month or so of research on that... along with more AGSON research as well, and sort my car, and, and, and .... and your travels, and value of experience in your videos etc, is highly valued here... a deep thank you Wal...

 

[WalnLiz]

Mmm... thanks... I rocked into Tibooburra decades ago two weeks prior to a Rodeo Weekend (exactly two weeks prior to, and camped in the desert to the west of the town in the boulders drawing and dreaming)... and when I came back to town, found no accommodation was available due to the Rodeo Weekend about to happen (unbeknown to me at the time) and thus, was going to sleep under the school when a resident graciously saw my intent and fed me with a meal and a bed... then … …next day I was outside the pub and was drawing the pub in pencil (still hav the drawing somewhere) and the pubs' cold shoulder attitude from the previous day was dropped like a Hot Rock noise because I could draw and paint (to the point of attitude change where I was almost a celebrity... lol..). but then it was about to rain buckets so the whole Rodeo Weekend was cancelled and I became part of that flurry of activity,....as all roads were about to be closed etc... and so, the next day I immediately ended up in Broken Hill via a hitch out in time to miss the flood... The whole place around Tib. is amazing, the colours of the ground, the horses, the people, and in the boulders I camped around, an iron plug stuffed up my trig point triangulation (that was completely haywire), as my compass was 30-40% out, ... so I scratched Star Chart directions on the ground with a stick, and discovered next day how deep the magnetic anomaly is there.. Anyhow... I am sure that you could write a book on your escapades as well... lol... I am about to buy some coils n 2 detectors of some kind... a VHF and a PI... and will do another month or so of research on that... along with more AGSON research as well, and sort my car, and, and, and .... and your travels, and value of experience in your videos etc, is highly valued here... a deep thank you Wal...

Tibooburra is certainly a memorable spot on the NSW map, and most who venture out there leave with a saddened heart that they have to go back to the big smoke. Gold is the secondary pleasure you get from such an environment, with the scenery and sunsets being the most memorable thing to take away. Good luck with your detecting and should you have any questions please don't hesitate to ask.....Wal.

 

[sam-u-al]

Tibooburra is certainly a memorable spot on the NSW map, and most who venture out there leave with a saddened heart that they have to go back to the big smoke. Gold is the secondary pleasure you get from such an environment, with the scenery and sunsets being the most memorable thing to take away. Good luck with your detecting and should you have any questions please don't hesitate to ask.....Wal.

Many Thanks Wal... right now I am in the mode of gathering info on the whole field of metal detectors, coils, EMI info, etc etc (which you and many others probably know off by heart...)… and currently am in the position of "just finding out what questions to ask"…
..... so... ha! … right now...
Your invitation is most welcomed here,
. . . but also right now, I have no idea what questions TO actually ask...
So... thanks again... much appreciative of your boundless generosity...
Ill get back to you when I may (actually have reached) a clear understanding of the answers that come back this way...
....cheers and good health by the campfire hey!
ps... At this stage I am devouring the Search Engine features (where ever I can) to find out what I do not know...
And, I will at some stage, share whatever clarity comes to me, within this forum and you can all fill in the blanks... that seems to be the best way...
Currently swaying into looking at more info on the Goldbug Pro, and the MineLab GPX4500... as well as Coils and gear that would cover the range of needs (that right now re soil types, moisture, noise and filters etc I am aware I have little clue of)… As I am aware that... one detector cannot do all jobs... and being a retired Tradie know quite well that tools and knowledge of HOW TO use tools is the key factor...
I just re-read the (first Pub. in 1931) book by Ion L. Idriess (reprint 1966 HB copy) of "Prospecting For Gold, Tin, Osmiridium, Platinum, Opals, with a chapter on Oil by Dr W. G. Woolnough... and in the old days they did it hard..gee... we are certainly blessed in 2022...
Cheers Wal....

 

[Moneybox]

I've never been to Tibooburra but I'm told the gold us usually very small, WalnLiz might find it differently but most of can't compete with their expertise.

I general the best metal detector for the job is the best you can afford. I just watched the field test at Tibooburra of the new yet to be released Garrett Axiom. It seemed to perform well there and in the same price range I would expect the Minelab GPX6000 to do a similar job. The GPX4500 is an excellent older design detector that is suited to a wide range of prospecting but you'd need to have a suitable coil for job. I have a nice little Whites GMT VLF detector but since buying the PI machines we've never used it when hunting for gold however it's an excellent treasure detector preferred over the Equinox. I think the Minelab SDC2300 should perform well there too but the GPX6000 has the advantage of being able to cover a lot more ground because of the larger coil size.

I hope this may be of some assistance in making your decision.