Hot Rocks

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aclayton80
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Hot Rocks

Post by aclayton80 » Sat Sep 08, 2018 6:55 am

Hi there,
I’ve been directing for about a year now, and I have a permission that’s next to a still used steam railway line. The field has loads of hot rocks as you would expect, but I was just wondering if anybody has and tricks for not digging them. I know the signal gets very skippy, but I’m scared of missing something.
Any tips will be appreciated.

Thanks Andy Clayton



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THE MOLE
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Re: Hot Rocks

Post by THE MOLE » Sat Sep 08, 2018 7:56 am

unless your machine is capable of knocking them out im afraid its all down to your ears and judgment
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Re: Hot Rocks

Post by Raymond » Sat Sep 08, 2018 9:31 am

Hi Andy the way I done was use a minelab with fbs and that got rid of it
I now have a equinox and it doesn't see it either,I have actually found
Good targets and coke in the same hole,the machine wasn't seeing
The coke at all!!!
Hope this helps ::g

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Re: Hot Rocks

Post by oldartefact » Sat Sep 08, 2018 10:29 am

aclayton80 wrote:
Sat Sep 08, 2018 6:55 am
Hi there,
I’ve been directing for about a year now, and I have a permission that’s next to a still used steam railway line. The field has loads of hot rocks as you would expect, but I was just wondering if anybody has and tricks for not digging them. I know the signal gets very skippy, but I’m scared of missing something.
Any tips will be appreciated.

Thanks Andy Clayton
If you could tell us what machine you have ... it would help the relevant machine experts give you some hot tips... Some tips from me ... often the hot rocks are on the surface, so train your eye to look for them poking through when you get a signal. Identify the numbers ... usually 25-30 on the Deus, so just ignore them, havent found a good item in that range yet. Hope that helps.
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Re: Hot Rocks

Post by aclayton80 » Sat Sep 08, 2018 10:38 am

Hi Raymond
I have a Garrett AT-max, not too sure if I can do that, I tried to set discrimination but the hot rocks are giving signals anything for 40 to 70 ish. Don’t want to miss anything.
I’ll look into it a bit more.
Cheers ::g

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Re: Hot Rocks

Post by Raymond » Sat Sep 08, 2018 11:25 am

Hi Andy I had the same problem with my nokta forscore hammy's and coke numbers were very close together so I would dig a bag of it each time I was out,in the end that's why I switched to minelab,that was the end of that problem, with most of the VHF machine's I find it hard to knock out coke and not the goodies with it, that's my experience anyhow!!
Good luck
Raymond

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Re: Hot Rocks

Post by Steevo45 » Sat Sep 08, 2018 12:38 pm

While on the topic of coke and hot rocks am I right in thinking that the black really light stones are from burning? Was out on some land a few nights ago trying to find my dads phone that he buried whilst digging ditches!! And in all the spoil we only found a load of these rocks and his phone so very little signs of human activity but i always believed these rocks were ploughed in waste from industrial burning????

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Re: Hot Rocks

Post by vladorado » Sat Sep 08, 2018 12:50 pm

My CTX3030 can eliminate the hot rocks signal only on Auto Sensitivity, on manual sensitivity it cannot GB them out. The automatic GB eliminates them. The manual GB does not on manual sensitivity. I started hearing the hot rocks after I started using the manual GB ( because the automatic GB tracing, traces the deep non ferrous signals out).
I always scrape away the top soil and this moves the surface ones. I use my Apex pick's magnet to pick them up. The deep ones I dig just in case. The hot rocks on the CTX3030 give nonferrous signal, but do not show on the target trace. Some can be pinpointed and some of them either do not pin point or null the pinpoint sound when the coil goes over them.
So - non ferrous signal with jumping numbers and target trace cursor, that do not pinpoint is a hot rock! All coins under a hot rock sound ferrous! I dig all ferrous signals in the vicinity of a hot rock.
I hope this helps!
Last edited by vladorado on Sat Sep 08, 2018 12:59 pm, edited 4 times in total.
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Re: Hot Rocks

Post by aclayton80 » Sat Sep 08, 2018 12:51 pm

I think they are from the old Steam traction engines that used to work the land ::g

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Re: Hot Rocks

Post by Steevo45 » Sat Sep 08, 2018 1:04 pm

That was my thinking too, but the site we where on was a marsh land that as far as know hasn’t ever really been worked, couple of Bronze Age boats once got dig up though ::g not that me or any one else will ever be able to search it as it’s a wetlands trust site we only went on to recover the phone, did try and not find it for a while hoping a axe head came up whilst searching 🤣

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Re: Hot Rocks

Post by Steevo45 » Sat Sep 08, 2018 1:06 pm

Apparently the golden mask detectors give a complete iron tone on coke, ive not got one but this is one of the reasons I’m tempted to get one

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Re: Hot Rocks

Post by fred » Sat Sep 08, 2018 1:58 pm

vladorado wrote:
Sat Sep 08, 2018 12:50 pm
My CTX3030 can eliminate the hot rocks signal only on Auto Sensitivity, on manual sensitivity it cannot GB them out. The automatic GB eliminates them. The manual GB does not on manual sensitivity. I started hearing the hot rocks after I started using the manual GB ( because the automatic GB tracing, traces the deep non ferrous signals out).
I always scrape away the top soil and this moves the surface ones. I use my Apex pick's magnet to pick them up. The deep ones I dig just in case. The hot rocks on the CTX3030 give nonferrous signal, but do not show on the target trace. Some can be pinpointed and some of them either do not pin point or null the pinpoint sound when the coil goes over them.
So - non ferrous signal with jumping numbers and target trace cursor, that do not pinpoint is a hot rock! All coins under a hot rock sound ferrous! I dig all ferrous signals in the vicinity of a hot rock.
I hope this helps!
Try manual ground balancing the CTX over the largest hot rock that you can find. This should eliminate them all although you might still get the odd negative signal. ::g This might even work for other detectors.

The Nox doesn't get coke in the Modes that I use but it confuses the hell out of the pinpointer if it is down the same hole as a good target. :D
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Re: Hot Rocks

Post by vladorado » Sat Sep 08, 2018 3:01 pm

The manual GB does not eliminate magnetic hot rocks on manual sensitivity, only on "AUTO". They give a nonferrous signal that fades rapidly when you lift the coil. That's why I get mostly surface hot rocks that are easily identifiable by scraping the surface inch of soil and with the pin pointer.
Thanks!
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Re: Hot Rocks

Post by fred » Sat Sep 08, 2018 3:54 pm

vladorado wrote:
Sat Sep 08, 2018 3:01 pm
The manual GB does not eliminate magnetic hot rocks on manual sensitivity, only on "AUTO". They give a nonferrous signal that fades rapidly when you lift the coil. That's why I get mostly surface hot rocks that are easily identifiable by scraping the surface inch of soil and with the pin pointer.
Thanks!
How odd, it used to work perfectly for me. ::g Must be a different setup anyway because I avoided Auto GB like the plague because of the sensitivity loss on really deep targets and for me the CTX was mostly about extreme depth on beaches. :D
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Re: Hot Rocks

Post by vladorado » Sat Sep 08, 2018 4:44 pm

Yes, it was your advise to use manual GB for maximum depth that I took on board. Now I too use only manual GB and sensitivity. And your type of shovel for the beaches. ::g
Thanks Fred!
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Re: Hot Rocks

Post by Ferrett » Sun Oct 14, 2018 1:49 am

I found when using the Nokta fors core in wet salty sand/mud, if the ID number is 95 / 96 I ignore it
as it is usualy coke ,

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Re: Hot Rocks

Post by sweepstick47 » Mon Oct 15, 2018 5:24 pm

garrettoldboy wrote:
Sun Oct 14, 2018 12:36 pm
hello, ok so what do MDF people think is the definition between coke and hot rock, ???? both must have iron minerals to give a metal detector the ability to register, but from my experience both give different readings, not that i dig much on my friends farm, but i could fill a skip with old iron ;;z
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Re: Hot Rocks

Post by sweepstick47 » Mon Oct 15, 2018 5:27 pm

A duplicated post by garrettoldboy has been removed.
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Re: Hot Rocks

Post by Koala » Mon Oct 15, 2018 7:12 pm

Coke is varied

Some have a strong negative reponce which gives a double beep when swinging over it


Some have a neutral reponce and don't cause an issue


Some have a strong positive reponce and will always give a strong reponce


At the end of the day its conductive and inter reacts with the magnetic fields from the coil.



This reaction alter differently with fequency which is why multi frequency machined handle coke better.


With the AT Pro you will have to be in Pro mode. With good headphone you will hear a difference on most coke. Good target gives a nice sharp beep. Coke generally gives a longer beeeeeep with a slower rise and fall to the sound. Also often sounds different with swing direction


Sensitivity too high will result in digging more.


In very bad fields its worth using your pinpointer to check the surface first.


I have been on fields that use to hold ploughing competitions. The lumps of coke are literally touching each other. By far the biggest problem is the masking effect if the coke. Coins liberally have to be on the surface.

On ploughed or stubble weather also plays a part. Worse when water logged. Often not great first thing in the morning ( dew )

Depending on your fields will depend on how much of a problem it will be.


Also some fields it only affects a relatively small area. Often a flat area where the traction engine would sit and have it fire box cleaned out.

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