Hotrocks and the SDC 2300

[Heatho]

Wally69 and myself went for a quick detect this morning and encountered an area which really looked excellent that I picked from Google Earth. When we got there I set up, started swinging and immediately got a very nice signal, the target was a Light Brown, Smooth ironstone looking hotrock, anyway I kicked it aside and next swing got another one which looked like a very Black Basalt which was Iron stained and had little Iron Oxide spots inside it.

These rocks were everywhere and every single swing produced one and they all gave a solid signal, Wally69 was finding the same with his SDC also. We were a few hundred metres from some old deep lead mines

This ground was virtually undetectable with SDC's, so I'm thinking about trying there again with my 5k in Enhance or Sens Smooth with the 11" mono or Sadie coil.

Has anyone else encountered such a difficult type of ground before? Have any 5k owners had any success with Sens Smooth or Enhance in such hotrock infested areas?

 

[Oldfella]

I have come across simular rocks with my 5000, I found that the Sadie can tame them, but you may have to lower the gain a fair bit.

Cheers

Edit = Forgot to mention I was using Fine Gold

 

[Guest]

Sounds like you found a basalt "hot spot". Its the only stuff thats troubled my SDC to date but while it was plentiful in the area I tried, I wasn't getting one every swing or anywhere near that. I was only getting the odd one every 10mins or so & all were pretty much on the surface + bantam chook egg size or bigger.
Have heard of some pretty bad places south of Bathurst for basalt & I think there was some hope the SDC may be the answer as other machines don't fair that well either. Looks like it isn't! :lol:
Best hope would be to experiment with the 5000 but the areas I have heard about hold deeper gold so to achieve missing the "hot rocks" may mean less depth anyway?
I have tried the 5000 in another similar area with fairly well scattered basalt & it ran similar I.e. the odd "hot rock" signal every now & again but nothing like you are describing. That was in fine gold with 11" mono & 14x7 NF - never tried other settings as it was infrequent so bearable & I got a couple there in fine gold so never worried about changing.

 

[Guest]

I found about half a dozen hotrocks at Windeyer and Hill End a few days ago.

They give off a nice smooth sound/signal. I bought them home to crush up and pan for research.

I tried to use the green ground balance button over one of them but it did not balance it out, come to think of it my manual gound balance attempts don't seem to change anything, almost like the green button does nothing.

I think hotrocks come with the territory and are not yet avoidable. My propointer sets off on the hotrocks as well.

 

[Heatho]

Thanks Old Fella, I'll try that, may even try the DD too if Sadie fails. I've found quite a few hotrocks with the 5k now and then but this spot was covered in them, maybe 5-10 per square metre, huge ones and small ones.

I think the SDC and 5k in Fine/Gold behave quite similarly with hotrocks with my limited experience, found a similar ratio at Wattle Flat between the 2 machines, Enhance rejects the ones there very well, though they give a broader tone, the ones at this spot today give a full overload near the coil almost like a coin rubbing on a coil.......

They are loaded with something, rockchip assay results nearby give a 70ppm reading of Zinc but surely thats not doing it and it does not state which rocks were sampled.

Will try the spot again and nearby as it just looks good and seems quite a bit of Gold was recovered from the general area, most difficult ground ever for me though.

 

[Oldfella]

Mate, if they are loaded with zinc, I don't think any Coil/Setting will help.
Best of luck.

 

[rc62burke]

Hey Heatho
That doesn't sound like too much fun!!!!
Why don't you take a few random soil samples to see if the ground holds some "Gold" that the SDC will find, this may help you to work out how much time you may like to persevere with the hot rocks!!
cheers
Lee

 

[Teemore]

Have samples of both at home the light sandy coloured 'stone' and the dark 'hot rock' , it's magnetic but the light sandy one isn't and may so traces of gold if crushed.
AND as Retirement Stone mentioned ...... I also don't think the ground balance button does anything on the SDC, it's a nice shade of green though ????
May have to check with Minelab to see if there's a method to test it ... may PM Nenad first.
Cheers T.

 

[Guest]

I found about half a dozen hotrocks at Windeyer and Hill End a few days ago.

If the Windeyer ones are basalt then they will be just hot rocks. Windeyer is the area where the SDC picks them up for me in one main spot in particular.
All the Hill End "hot rocks" I have found with the SDC so far have contained gold A couple I nearly chucked as they were large, high in ironstone content & "ugly" quartz so I thought they were just hot rocks. I don't discount anything the SDC signals on now - other than the basalt. :lol:

I tried to use the green ground balance button over one of them but it did not balance it out, come to think of it my manual gound balance attempts don't seem to change anything, almost like the green button does nothing.

I couldn't ground balance the basalt out either.
The auto tracking does a pretty good job in my opinion & won't track out small signals like some tracking can/will. The manual button, I have found, probably doesn't need to be used that much. I find that I am more doing it out of habit rather than necessity. It is good to get the machine settled quickly in variable ground or if the threshold gets a bit unstable after a target etc. but there's probably no real benefit in doing it frequently if the threshold is staying stable, which if the button isn't doing anything/much sounds like it would be.

 

[Heatho]

I think you might be right Matt, hadn't heard of that before but sounds about right as a Basalt hotspot. Same here also, most places get the odd one but not like this. Will have to experiment with a couple of coils. The SDC is not the answer to it at all, still a great unit though. Was Dog Rocks SF

Retirement Stone, yeah I could'nt GB these ones out either, no chance.

Old Fella, thanks again, I guess that is probably it then.

Lee that could be worth a go, thanks.

 

[Oldfella]

Keep dumbing the machine down until it becomes usable, you will miss small gold in doing so, but because the area is such a problem, I would guess that every one else has given up in the past leaving the possibility for a nice size nugget or two for your taking

 

[Guest]

I have read that the reason some basalt signals & not other bits is all to do with the iron content with some particular rocks, which seem to be a minority in most cases, having a higher content then others so obviously signal. It appears you may have found an area where all of the basalt has a high iron or other metallic content so the majority of rocks signal.
Playing with the GPX settings will be the go but from what I can gather there are some spots around there that are a source of frustration regardless of machine. Like Oldfella said if you can come up with something workable then you never know what others have left behind by giving up in these areas.

 

[Heatho]

Very true, there were a few detector holes but not many, so others may have given up. Maybe for good reason, was very frustrating. Probably better spots to try but if anyone can ping a nugget there they really deserve it.

 

[wooly]

I tried to use the green ground balance button over one of them but it did not balance it out, come to think of it my manual gound balance attempts don't seem to change anything, almost like the green button does nothing.

Totally agree with this. The green balance button never seems to make any difference. I have been wondering if I had a faulty unit!!!

 

[Guest]

Is the threshold unstable beforehand?

 

[Narrawa]

Fine gold and a Sadie will only make hot rocks more problematic. The smaller the coil the more pronounced they will be. . You need to go higher up the mineralization chain to either Enhance or S/smooth.
But just remember, the smaller the coil, the more powerful its field....combo it to the wrong timing and you could walk away thinking the ground is misbehaving far to much. What your actually doing is..over gaining the detector.
Larger coils with one of the smooth timings, will lower the sensitivity to hotrocks and surface mineralization compared to using smaller coils.

 

[Oldfella]

Narrawa, you are probably spot on in your advice.
My suggestion in using the Sadie and winding down the gain was only through my personal experience where I had encountered a simular hot rock problem near Hill End recently. Out of the small amount of coils that I had on hand at the time, the Sadie at Fine Gold/Low Gain worked best for me.

I will try your approach next time I encounter a simular problematic area

Cheers

 

[Narrawa]

Oldfella, if it works for you at the end of the day, let no one tell you otherwise. I know Hill End pretty well, and the ground has many types of mixes that will teach you how to combo coils and timings. It was my first port of call for training folk there due to the different ground types. You could say that while im in WA, im not doing it as hard as i was when i detected the Central West, because over here its cream compared to places like H.E.

 

[Heatho]

I tried to use the green ground balance button over one of them but it did not balance it out, come to think of it my manual gound balance attempts don't seem to change anything, almost like the green button does nothing.

Totally agree with this. The green balance button never seems to make any difference. I have been wondering if I had a faulty unit!!!

It does feel that way sometimes but it does work, 2 or 3 pumps up and down and it's ground balanced usually.

 

[Teemore]

In regard to SDC ground balance asked PhaseTech (Nenad) and he kindly and knowledgeably responded with ......

"definitely not an issue, just handles the ground very effectively and the auto tracking means it will very rarely go out of balance. You could try ground balancing in the air for 15 secs while holding in the gb button. That might throw the balance enough when you lower the coil to the ground you hear it's out of balance."

Thanks Nenad.

Settles it for me, back to detecting,
Cheers T.

Oh, think it's also time to stop extolling the virtues and capabilities of the SDC, don't want too many others out there spoiling the party.