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Targets In Shale


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Are you using a VLF or a PI? I recently got a screaming target in dry clay/shale (both VLF & PI machines) that passed the iron discrimination test (i.e. it wasn't iron). The locality was known for big nuggets so I got all excited. Turned out to be graphite. It could be that there's some carbonaceous or graphitic material intervals in your shale. If you get a black streak if you rub it on a hard rock that's likely your source.

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You never know what a signal is till it is eliminated. One day we went prospecting a couple of hundred meters from a patch that I had found. My prospecting mate and our wives were detecting the area when my mate got a signal near a tree. After he had dug over a foot deep he said it must be the tree sap giving his VLF the signal. As he had given up I said let me test it. To keep it short I dug a 2 Oz. nugget up for him. After he let his wife have a feel of the weight he handed it back to me. I looked at him and said you found it so it's yours. Well we checked close and around the nearby trees. I got a great signal on one tree and went right around it. I thought it must be under the trunk of the tree as the strength was about even all the way round . I lifted the coil off the ground to dig but the noise got a lot louder it peaked about 2½ above the ground. What we found was that the tree had grown around a horse shoe. Totally hidden by the bark. After exposing the horse shoe, I said to my mate now it is your turn to dig it out with a smile. 🤣

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Ar Tibooburra far western New South Wales in Oz, partner was detecting on a slate/shale bedded hill with a vertical orientation. I could not handle it. You dig up a signal, most likely very small gold and the slate would break up and the gold would find another nitch of vertical  slate/shale to fall into.... remove the surface shale and start again....me not again. But, SWMBO was using a small paint brush to coax the small gold out of the cracks... and I left her to it.

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Hmmm, a strong, localized signal, embedded in (vertically oriented?) shale, in an auriferous creek where you "have done well" on gold in the past. Gosh, personally, i'd say that it would be a good idea to  JUST DIG IT! HH Jim

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16 hours ago, oldmancoyote1 said:

Oxidized sulfides often resemble gold when viewed with a metal detector.

Would you give an example or two of minerals that fit this profile?

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11 hours ago, GB_Amateur said:

Would you give an example or two of minerals that fit this profile?

Locally, it's pyrite that usually forms an iron stain or lumps of iron oxides, but the situation is very complicated.  Example:  Some of the local pyrite contains a little gold.  When the pyrite oxidizes, it forms an acid.  If there is some manganese present and some salt (often the case in black shales), any gold may go into solution.  The gold can then precipitate as very thin films on shale or as valuable spongey pocket gold.  I don't really know how to judge which is the case without digging up the shale.  After digging up a lot of oxidized pyrite without any visible gold, I have given up metal detecting the local black shale.

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I hit the creek again and it turns out the spots where I am getting signals aren't in the shale. It's a harder black or dark gray stone. When I pursued one of the signals wit miy hammer and chisel I opened up a pocket that had a bunch of rust in it. The target was found with my GPX. 

Sorry about the confusion with the shale. That's where I thought it had been. Thanks for all the comments.

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  • 2 weeks later...
On 2/7/2022 at 12:52 AM, Machineman said:

I have been working a creek and have done fairly well. There have been at least 3 spots where there seem so be a strong signal in the bedrock , which is mostly shale. I keep a rock hammer and chisel in my bag and have tried to dig some out. I feel like it's just a particularly hot spot of ground, but I dont know that it is, they seem vary localized. Any thoughts?

Could be mineralization, could be a nugget, bullet.... you never will know for sure until it's been excavated. All we can do here is speculate. If you dig enough of them in a given area, the answers become clearer in the future.

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