Rocks that set off metal detectors/pinpointers

[Bucket Lister]

Is there a list of rocks & minerals that will set off metal detectors?
I found such a stone today--it was infuriating!!!! 🤬

After several minutes of sifting through substrate with my pinpointer expecting to find another rusty square nail, all that was left was one stone. It doesn't set off the pinpointer like being in contact with a piece of metal, but it does set it off--like being a few inches away.

No, it's not being set off by my keys or pocket change--BT-DT. 😳

 

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[Midden-marauder]

Is there a list of rocks & minerals that will set off metal detectors?
I found such a stone today--it was infuriating!!!! 🤬

After several minutes of sifting through substrate with my pinpointer expecting to find another rusty square nail, all that was left was one stone. It doesn't set off the pinpointer like being in contact with a piece of metal, but it does set it off--like being a few inches away.

No, it's not being set off by my keys or pocket change--BT-DT. 😳

I mostly get grief from bits of magnetite or similar, that's why I'll sweep holes with a pick up magnet, actually saves some headaches. I've been trying to find a comprehensive list of these hot rocks but no luck as of yet. I know red brick will do it but that's potentially useful in my opinion

 

[Midden-marauder]

This has a write up but I don't know if it's a comprehensive list, I think there's a lot of potential offenders here

Hot Rocks

How To Eliminate Audio Responses To Hot Rocks

www.metaldetectingworld.com

 

[Bucket Lister]

I mostly get grief from bits of magnetite or similar, that's why I'll sweep holes with a pick up magnet, actually saves some headaches. I've been trying to find a comprehensive list of these hot rocks but no luck as of yet. I know red brick will do it but that's potentially useful in my opinion

Not magnetite, hematite, or pyrite; I know them by sight & feel. Hematite is most common in these parts, but not usually this shallow. I'm not so familiar with limonite or siderite, but they're not usually found in this area.

Whatever this is, it's fairly lightweight (but not slag).

 

[ARC]

Talk about frustrating rocks i just throw as far as i can away from my detecting areas every time i find one...
There are these strange little quartz rocks with gold looking lines in them that fool me every time.

Here is an example of one of these damn rocks...

:P

 

[Bucket Lister]

Talk about frustrating rocks i just throw as far as i can away from my detecting areas every time i find one...
There are these strange little quartz rocks with gold looking lines in them that fool me every time.

:P

Can't do that. Permission is in the village proper; throwing a rock would be unwise. I'm keeping this one for now.

Rutilated Herkimers? Ever seen one polished into a crystal ball? Gorgeous.

 

[Midden-marauder]

Talk about frustrating rocks i just throw as far as i can away from my detecting areas every time i find one...
There are these strange little quartz rocks with gold looking lines in them that fool me every time.

Here is an example of one of these damn rocks...

View attachment 2150300

:P

Darn those pesky hot rocks

 

[Midden-marauder]

Not magnetite, hematite, or pyrite; I know them by sight & feel. Hematite is most common in these parts, but not usually this shallow. I'm not so familiar with limonite or siderite, but they're not usually found in this area.

Whatever this is, it's fairly lightweight (but not slag).

Yeah, I find a fair bit of ferromagnetic detritus in some spots but honest to God hot rocks are rare enough for me that if I find one I actually frequently keep it. Thus far I can say I've found one confirmed hot rock and it was large, part of the remains of a demolished structure, I think it was a hunk of basalt but I'm no rock expert. Eventually I'll end up with a jar or such rocks, magic metal detector stones, they're kinda neat despite being annoying

 

[Bucket Lister]

Yeah, I find a fair bit of ferromagnetic detritus in some spots but honest to God hot rocks are rare enough for me that if I find one I actually frequently keep it. Thus far I can say I've found one confirmed hot rock and it was large, part of the remains of a demolished structure, I think it was a hunk of basalt but I'm no rock expert. Eventually I'll end up with a jar or such rocks, magic metal detector stones, they're kinda neat despite being annoying

The hot rock I found is much smaller--I would say less than two cubic inches--and just part of the topsoil.

It's got me thinking though... If someone were interested in actually hunting/collecting these hot rocks, a bank run gravel pit might be worth detecting.

 

[Midden-marauder]

The hot rock I found is much smaller--I would say less than two cubic inches--and just part of the topsoil.

It's got me thinking though... If someone were interested in actually hunting/collecting these hot rocks, a bank run gravel pit might be worth detecting.

You'd think I'd find more given that I'm prone to searching xeriscape patches in some locations but nothing there so far. Maybe around some of the volcanic features in my state....

 

[Bucket Lister]

Thanks for expanding my vocabulary!

 

[Ism]

A picture would be helpful. You sure it isn't a clinker (burned coal residue)? I find them in farm fields where old houses used to exist, looks like a black rock but extremely light. Clinkers can have a high iron and/or aluminum content and often set of the detector.

 

[Bucket Lister]

A picture would be helpful. You sure it isn't a clinker (burned coal residue)? I find them in farm fields where old houses used to exist, looks like a black rock but extremely light. Clinkers can have a high iron and/or aluminum content and often set of the detector.

Yes, I know what clinkers are; I've heated with coal. That's how I know it's not.

 

[Bucket Lister]

This has a write up but I don't know if it's a comprehensive list, I think there's a lot of potential offenders here

Hot Rocks

How To Eliminate Audio Responses To Hot Rocks

www.metaldetectingworld.com

Mystery solved. After reading the above and cleaning it up a bit more (brushing off the caked-on silty soil that clogged the layers) it was obvious.... GRAPHITE.

Graphite isn't found around here, so it kind of threw me. There are no matrix components either.

Definitely keeping this for the old rock collection--it's better than the piece of graphite I had previously. 😁

 

[pepperj]

I mostly get grief from bits of magnetite or similar, that's why I'll sweep holes with a pick up magnet, actually saves some headaches. I've been trying to find a comprehensive list of these hot rocks but no luck as of yet. I know red brick will do it but that's potentially useful in my opinion

I have dug up red, tan brown, black brick and have never experienced the brick setting off the detector or the pin pointer.

 

[pepperj]

Mystery solved. After reading the above and cleaning it up a bit more (brushing off the caked-on silty soil that clogged the layers) it was obvious.... GRAPHITE.

View attachment 2150418
View attachment 2150419

Graphite isn't found around here, so it kind of threw me. There are no matrix components either.

Definitely keeping this for the old rock collection--it's better than the piece of graphite I had previously. 😁

Old coke will do it also.

 

[ARC]

Old coke will do it also.

What about Pepsi ? ? ?

Mountain Dew ? ? ?

 

[robertk]

What about Pepsi ? ? ?

Mountain Dew ? ? ?

Only if they're in aluminum cans. The glass bottled kind doesn't work.

 

[Midden-marauder]

I have dug up red, tan brown, black brick and have never experienced the brick setting off the detector or the pin pointer.

It's weird, my minelab pinpointer goes off on it but only if there's more than a few bricks present. Always red fire brick, I actually found a buried brick path on our property because of it. Those minelab pro find pinpointers are temperamental but pretty damn sensitive, if I super tune it with a washer I can actually detect iron utilities buried a foot down in some cases. Just right for someone who hunts with just a pinpointer 95% of the time, just gotta make sure I pack in my EMF meter, power lines and various sources cause reasonably bad falsing on this unit.

 

[Bucket Lister]

Those minelab pro find pinpointers are temperamental but pretty damn sensitive, if I super tune it with a washer I can actually detect iron utilities buried a foot down in some cases.

Is that washer-tuning trick confined to Minelab pinpointers?

I haven't run into any brick yet that I can think of, but now that I know about hot & cold rocks (🤦🏼‍♂️), I'll keep it in mind.

In the back of my mind, I figured something like magnetite might do it (wasn't sure about hematite), but I don't run into either of those either.