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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[Chilli]

Yeah, I've found that it's red fire brick pretty specifically. I've wondered if it depends on the era the brick comes from but not being a brick expert (even though I'm an expert on things like nails and screws) I can't tell one from another. It's red fire brick, looks old, possibly recycled, it could have been fired five years ago or five decades ago, it's currently beyond me, makes the pinpointer go bonkers, that's all I got

Hi. The ones here are from the late 1800s to early 1900s.
After looking it up and following a hunch, they use iron oxide in them to give the red colour. Im betting its the iron oxide.

 

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[Almy]

MM: Thanks for the pinpointer tips! I understand better how you use it and it will help me. I'll have to review about super tuning - I know mine has that capability but haven't used it. I go to a 1650s site that has a bank washing into the sea. Have never found anything there but maybe........ I'll go there again this year. It is the site of an early French church.

 

[Bucket Lister]

Yeah, I've found that it's red fire brick pretty specifically. I've wondered if it depends on the era the brick comes from but not being a brick expert (even though I'm an expert on things like nails and screws) I can't tell one from another. It's red fire brick, looks old, possibly recycled, it could have been fired five years ago or five decades ago, it's currently beyond me, makes the pinpointer go bonkers, that's all I got

Not just era, but locale as well. Bricks were--and can be--made anywhere there is clay.

Hi. The ones here are from the late 1800s to early 1900s.
After looking it up and following a hunch, they use iron oxide in them to give the red colour. Im betting its the iron oxide.

I'm wondering if it's just a matter of whatever clay is/was used in making the bricks containing a high(er) level of iron/hematite.

Red color/iron oxide = Hematite (Fe2O3)laden clay.
Iron oxides may be a natural component of--or added to--the brick clay.

I think fire bricks may be a red herring, though red bricks may not be..

 

[Midden-marauder]

MM: Thanks for the pinpointer tips! I understand better how you use it and it will help me. I'll have to review about super tuning - I know mine has that capability but haven't used it. I go to a 1650s site that has a bank washing into the sea. Have never found anything there but maybe........ I'll go thereo again this year. It is the site of an early French church.

Super tuning is more commonly known as the coin trick. You take a small bit of metal, a coin for example, slide it down the shaft of the pointer until you get to the spot where it stops beeping, nudge it a hair further down past that point and hold it in place. Without explaining why this works it increases the sensitivity of the detector, so much so that it can double the reach in some cases particularly on larger targets I.e. bigger than a penny. It's a cool trick for sure but it of course can't help with target id, just that a target is there. I use it mostly when I'm trying to pinpoint deeper targets found with the regular detector. It's what has allowed me to locate utilities at 12+" using only the pinpointer so it really does make a meaningful difference in terms of depth

 

[Almy]

MM thank you for the tip about super tuning. I'll try it. Yesterday I was out with my regular detector and tried scanning areas with the pinpointer where the detector gave a signal. The target had to be within about 1.5" of the surface for the pinpointer to signal it. That wasn't very promising but I'll try the super tuning next.

 

[Midden-marauder]

MM thank you for the tip about super tuning. I'll try it. Yesterday I was out with my regular detector and tried scanning areas with the pinpointer where the detector gave a signal. The target had to be within about 1.5" of the surface for the pinpointer to signal it. That wasn't very promising but I'll try the super tuning next.

The size of the target will determine range, simply put, it's much the same as a regular detector. When I went shopping for a pinpointer I went through a LOT of reviews and ultimately I settled on the pro find series simply because I knew I'd be using it by itself so I wanted whatever had the greatest reach. At this point I might recommend nokta though I can't say I've used it, the user reviews in some cases suggest it has better reach and other cool features. For now I'm gonna keep using minelab, it's greatest virtue is also it's greatest flaw for many, it's hyper sensitive and it's 360 degree. It falses out a fair bit especially in close proximity to sources of EMF, super tuning it can cause a bit of falsing as well though not so bad as to make it beyond use, you just gotta get used to the things quirks, maybe sometimes double check the signal if there's doubt or power lines near at hand. I'm sure your Garrett is just fine, I'd experiment to see how far you can push it around the house on a few different sized targets. Using a bigger piece of metal to super tune gets you better reach, up to a point that is. I settled on a large fender washer beaten into a ergonomic curve for mine. I tried various metallic objects to see what got the best reach and the washer works the best without causing unworkable problems in use. A quarter may get you better range than a penny will, it's all about a particular threshold of metal volume. By super tuning you're essentially increasing the size of the intended target by adding a little more metal to the situation. The more metal there is just beyond the reach of the pinpointer the more it super tunes, again, up to a point. I'd experiment with it to get best results

 

[Midden-marauder]

MM thank you for the tip about super tuning. I'll try it. Yesterday I was out with my regular detector and tried scanning areas with the pinpointer where the detector gave a signal. The target had to be within about 1.5" of the surface for the pinpointer to signal it. That wasn't very promising but I'll try the super tuning next.

Oh, a caveat: you wanna make sure your pinpointer is ON first before attempting the super tune trick, on and adjusted to max sensitivity. If you hold a piece of metal within detecting range WHILE the pinpointer is powering up you'll actually DETUNE the pinpointer. If you hold a bit of metal right next to the coil and fire it up it'll detune it to the point where it won't detect metal of any sort, especially small targets. You can use this principle to ground balance to a limited degree by putting the coil on or in the ground and then firing it up, it'll reduce sensitivity to elements in the dirt to a degree. Just an afterthought there. Good luck!

 

[Chilli]

Hey guys. These are the culprits I mentioned that are a pain.
These would easy be from the mid 1880s here on our goldfields. And they are a nightmare to detect amongst. Took this pic on our walk today.

 

[Midden-marauder]

Hey guys. These are the culprits I mentioned that are a pain.
These would easy be from the mid 1880s here on our goldfields. And they are a nightmare to detect amongst. Took this pic on our walk today.
View attachment 2161572

Yep, a single brick usually doesn't do it for my gear but a number of them together will for sure

 

[Bucket Lister]

Yep, a single brick usually doesn't do it for my gear but a number of them together will for sure

When mine set off my detector, I was right on top of it--maybe 1" under. Pinpointer usually has to be in contact--sometimes within 1".

 

[Almy]

MM, thanks for your continuing tips!

 

[Midden-marauder]

MM, thanks for your continuing tips!

Any luck pinpointing there? It's not the most efficient method of covering big areas for sure though I swear using my regular detector isn't so much faster unless I'm trying to cherry pick for coins. I end up stopping to dig targets about as frequently and in some cases at greater depth which makes up for any time saved lol. If all I was trying to do was survey a site for metal targets and pushing flags in the ground it'd go pretty fast but until I attempt to map the utilities, which may become necessary unfortunately, metal detecting isn't a speed game. I find approximately as much with just the pinpointer, the only problem is that it's not the most ergonomic approach. Bent over at the waist, dragging it in grids across the area gets tiring fast. Any finds to report?

 

[pepperj]

I have a mid 1800s brick yard.
I cleaned all the glass, black organic material out of the clay pit.

Then dug it deeper so I could have a water source for my garden/berry patch.
Pure blue clay.

When we dug for the waterline we hit the bricks.

When I till I hit pieces of bricks.
When I detected the rubble piles, it didn't set off the detector or PP.

I detect around bricks at just about every permission and have yet to hear one give off a signal.
If the PP sensitivity is too high, then just pressing it on the dirt will set it off.
So maybe that's why you folks are detecting brick, the sensitivity is too high.

I have had a high tone for iron if certain rocks are on top or next to the iron.

 

[Chilli]

I have a mid 1800s brick yard.
I cleaned all the glass, black organic material out of the clay pit.View attachment 2162472View attachment 2162473View attachment 2162474
Then dug it deeper so I could have a water source for my garden/berry patch.
Pure blue clay. View attachment 2162471

When we dug for the waterline we hit the bricks. View attachment 2162470
When I till I hit pieces of bricks.
When I detected the rubble piles, it didn't set off the detector or PP.

I detect around bricks at just about every permission and have yet to hear one give off a signal.
If the PP sensitivity is too high, then just pressing it on the dirt will set it off.
So maybe that's why you folks are detecting brick, the sensitivity is too high.

I have had a high tone for iron if certain rocks are on top or next to the iron.

What on earth was in that oil bottle?
Our bricks where I am go of on Vlfs and Pulse Induction. More so Vlf but still do on PI. If you turn the sens down the signal gets weaker, but all the signals do following suit. It never stops them being detectable. Mine here are not an overload signal they are just mongrel red detectable bricks 😆
I guess there are various types that have similar colour but made different so some don't register. I hate our red bricks 🫤

 

[pepperj]

What on earth was in that oil bottle?
Our bricks where I am go of on Vlfs and Pulse Induction. More so Vlf but still do on PI. If you turn the sens down the signal gets weaker, but all the signals do following suit. It never stops them being detectable. Mine here are not an overload signal they are just mongrel red detectable bricks 😆
I guess there are various types that have similar colour but made different so some don't register. I hate our red bricks 🫤

Just another famous snake oil.

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[$MELTER-1]

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. 😳

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 don't know how to send the link but just type it in I box.its got some good info.

 

[Surf_Pirate]

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

throw those my way ARC

 

[Midden-marauder]

I have a mid 1800s brick yard.
I cleaned all the glass, black organic material out of the clay pit.View attachment 2162472View attachment 2162473View attachment 2162474
Then dug it deeper so I could have a water source for my garden/berry patch.
Pure blue clay. View attachment 2162471

When we dug for the waterline we hit the bricks. View attachment 2162470
When I till I hit pieces of bricks.
When I detected the rubble piles, it didn't set off the detector or PP.

I detect around bricks at just about every permission and have yet to hear one give off a signal.
If the PP sensitivity is too high, then just pressing it on the dirt will set it off.
So maybe that's why you folks are detecting brick, the sensitivity is too high.

I have had a high tone for iron if certain rocks are on top or next to the iron.

I'd say you were right about this but it really is brick that sets off my pinpointer, a single brick won't but if there's more than two or three it will. My pinpointer is pretty damn sensitive, this minelab pro find. That particular line of pinpointers is known for it's sensitivity so it may be a situation where some machines will react to brick while others won't. Just depends I guess. Nice bottle! I love a good old bottle as much if not moreso than an old coin!

 

[Bucket Lister]

Any luck pinpointing there? It's not the most efficient method of covering big areas for sure though I swear using my regular detector isn't so much faster unless I'm trying to cherry pick for coins. I end up stopping to dig targets about as frequently and in some cases at greater depth which makes up for any time saved lol. If all I was trying to do was survey a site for metal targets and pushing flags in the ground it'd go pretty fast but until I attempt to map the utilities, which may become necessary unfortunately, metal detecting isn't a speed game. I find approximately as much with just the pinpointer, the only problem is that it's not the most ergonomic approach. Bent over at the waist, dragging it in grids across the area gets tiring fast. Any finds to report?

My back hurts just thinking about it... 😓😢😭

I would think hunting with just a pinpointer would severely limit depth--even if the pinpointer were supercharged (I forget the term).

Any time I have (accidentally) detected with only the pinpointer (like when laying it down and it goes off), the target has always been ≤ ~3". Most of my targets are deeper than that. I'm also beginning to be able to tell more about a target from the sounds, numbers, and other subtleties that I cannot discern with just the pinpointer.

metal detecting isn't a speed game.

I didn't think so either until I went to my first MD event with a seeded surface hunt. 🤣
Even then, hunting with just a pinpointer wasn't necessarily advantageous; using the detector in pinpoint mode was faster.
I think I may still have some unresolved feelings about that whole situation...

 

[Midden-marauder]

My back hurts just thinking about it... 😓😢😭

I would think hunting with just a pinpointer would severely limit depth--even if the pinpointer were supercharged (I forget the term).

Any time I have (accidentally) detected with only the pinpointer (like when laying it down and it goes off), the target has always been ≤ ~3". Most of my targets are deeper than that. I'm also beginning to be able to tell more about a target from the sounds, numbers, and other subtleties that I cannot discern with just the pinpointer.


I didn't think so either until I went to my first MD event with a seeded surface hunt. 🤣
Even then, hunting with just a pinpointer wasn't necessarily advantageous; using the detector in pinpoint mode was faster.
I think I may still have some unresolved feelings about that whole situation.

So my thing about it is just this:

If I'm out on a designated relic hunting adventure then yes, I have my big coil along and will use it in the typical way. The reality of my situation is that I'm often too busy to spend much time doing metal detecting specifically. My girlfriend and I go out adventuring every week, often we're in remote or hard to reach locations. We engage in foraging, scavenging, wildlife photography, relic hunting and other exploratory pursuits. We're equipped to do a number of different activities in the field and it's absolutely a game of opportunity, right place at the right time. Those opportunities do include limited metal detecting. I pack a lot of gear in, all the stuff we need and use, I have no room in my kit for a full sized detector when we're out there. I need quick and dirty gear that fits on my already bristling utility belt and the pinpointer fits there beautifully, I can just have it out fast if we come upon a promising looking spot. Actually a large percentage of the metal objects I find are only with the pinpointer, I've turned up some reasonably old relics with it for sure. Many places we go have seen little, if any modern development which often means any relics are often closer to the surface, if not right on the surface making a pinpointer a more viable searching tool. The simple reality is that I don't do sufficient metal hunting in particular to warrant bringing in big kit every time, I go equipped for general recovery and recon and a large percentage of materials recovered aren't even metal, they're organic in origin. There's more I could say regarding why I go about it in that way but it boils down to logistics honestly. If I have time and space to do metal detecting as the primary activity then i pack in the big coil otherwise it's pretty eclectic, no telling what may end up in the recovery bag, medicinal or edible herbs, cool rocks, dead insects in good condition, little trinkets from some past, baby red squirrels, snakes in need of rescue, old bottles, fossils etc. We break for anything cool we happen across and the fact of the matter is that metal objects only make up a small percentage of items collected. Folks on this site see only a sliver of what I recover out there, for a start I'm getting very selective about the types of metal objects I'll even bother with, for a second so much of it isn't what I think most folks here would deem "treasure" even if it is of value. I won't bother posting images of the big bushels of wood betony, mullein, verbena, wild strawberry, yarrow, the pinecones (for the aforementioned red squirrel), Osha, rose hips, cleavers, wood sorrel, gentian, wild chives, parsley and etc. etc. they aren't relics exactly.

99% of the time I don't have time to grid large areas, I choose hot looking spots to detect and if it yields something cool, awesome, if not, then oh well, next time. We're not leaving this place empty handed regardless of what was found and how. Metal detecting is just one tool for the field, not necessarily the end game at least when we're out in the sticks tromping around. I get out to metal detect in more committed ways in the cooler months and for that I'll use my regular detector, pinpointer of course lol and even a magnetometer if I come across a possible BIG target. You might say it's a meta-hobby for me in most settings lol. It might seem unlikely but overall I'm kind of impressed with the things I've found only pinpointing, depth can matter but location seems to be a bigger factor in terms of what I find or that's been the experience thus far.
All that being said I'm ready for fall, I'll get out on a few dedicated metal hunts then and we'll see if I can't rustle up a neat artifact or two!