Early Days on gold nuggets.

[Bobbylikesgold]

Tried the F75 out on a goldfield for only a few hours, it was a one day trip with a long drive.

I'll try my best to describe what happened in the small amount of time my friend & I spent detecting a field.
Me F75 , him Whites Goldmaster 2 with 6"DD coil.
This field is remote, desert country, low hills with quarts screw en ground, old shafts into hard rock abound.

We were both eager to just jump out of the 4x4 an start sweeping, but sanity prevailed , our small match head sized nugget was placed on the ground to test after we both ground balanced,the mineralisation was high. (Setting was all metal motion with just a background threshold )
Sensitivity was set at 70 on the F75 & about the same on the Whites.
Well almost every second wave produced a signal like the test nugget, that sharp fzee fzee with repete sweep, on digging the signals some just disappeared & some were pea sized little hot rocks so frustration started to set in, I then would only dig the bigger signals that turned out to be bullets & boot tacks, so switched over to JE mode with disc set at 6 manuel ground balanced, rechecked our test nugget yep a clear zip zep signal yep its all OK, so started to sweep again , well what a huge difference I could now walk some 20 to 30 feet before getting a signal, the tone of these was a little different just a tad more confusing, on digging they were small hotter rocks.

I have taken some of these smaller hot rocks home so as to get a better understanding, NO we didn't get any gold this trip, but if we had dug every signal maybe.

My conclusion is the F75 tells you everything under the coil , you need to interpret whats what.

 

[MattR]

Hello Bobby. Thanks for the report.I hope you enjoyed the day despite the lack of hoped for results.

Can you answer me some questions?

Your ground balance figure, you didn't quote that, nor Fe graph readings (if any).

I would be very interested to gain some knowledge of such site data.

Why did you GB manually? Was 'fast grab' impossible?

What was the reading from your test nugget when placed on the ground, as compared to its 'in-air' value?

What are your thoughts now about searching in 'all metal motion' as compared to 'motion discrim' ?

Can you list the readings from the rock samples you brought back?

Well Bobby, there's a bit of home work for you. Maybe we can develop some ideas for the next trip out there. You will need a kit-bag full of patience, but let's hope you are rewarded next time, for such a long trip............Best wishes...MattR.UK.

 

[Bobbylikesgold]

Hello Matt, I'll try & answer those questions, firstly the Fe graph was 0.3 same as the ground in my own yard .
The reason to do a Manuel GB is that you can override the auto setting so as to be a bit more positive e.g. the GB was 68 so I made it 69.
Had to do these tests at home as I wasn't paying attention to the numbers, but my ground is the same FE graph.
Test nugget on ground all metal motion, reads 10 to 12, in the air 20,22 .
Threshold set at 0.
In JE mode the nugget on ground was 10 with a low tone ( tones was set at 3 ) but in air is 22 with a high tone.

Now the hot rocks.
In all metal motion 2 out of three gave no visual number yet there was a audio signal, the one that did was 98 !!
In JE mode no signal on 2 rocks but that same third rock signaled with a low tone & visual ID of 13 .

The all metal motion mode is the best choice for nuggets if the conditions allow, if not then JE mode with low disc & sensitivity set as high as the ground will let you.

Thanks for asking the questions as I have now found out that when I hear a signal using all metal motion & there is no visual number signal I wont dig that hot rock anymore.

Regards Bobby.

 

[Tinfoil]

n/t

 

[Tinfoil]

n/t

 

[Bobbylikesgold]

Hi Tinfoil, yep your right about that, most wont, I've got one that signals on pinpoint.
Fixed my own machine, think it was internal connections problem, but its better then ever now !

Regards Bobby.

 

[thompy]

Bobby i know my T-2 seems to do a lot better on the hot rocks in discriminate mode, I run it between 4-10, most of the hot rocks around the goldmines here are quite large. when i get out of this general area, there much smaller, no real gold yet

 

[vlad]

n/t

 

[Bobbylikesgold]

Thompy good the know about the T-2 on those hot rocks using disc , for those hunting small nuggets using the F75, I will need to do some testing , thank-fully the Audio & Visual are a separate signal.

Its great to know when you get a threshold wobble signal using all metal motion mode , then check the visual number read out, looks like most hot rocks show a plank, then don't dig.

Fisher have said that the Audio & Visual are separate signals, more information for the user.

Bobby.