What's Magnetic, But Not Picked Up By A Metal Detector?

[toadskin]

This could well be a stony iron meteorite. Some, although slightly attracted to a magnet, won't give a signal on a detector. Don't overly damage it or wet it. If you can grind a small window in the surface you may see some silver flecks on iron/nickel. Hopefully you have the GPS co-ords for the find. Let me know how you go.

 

[Hawkear]

Hello everyone... Good question for you all; What kind of metal is magnetic, but my detector won't pick it up? ickshovel:

Hi Big.nug.business.
Just revisiting your thread and wondering if you've had any resolution on the magnetic but non detectable "metal" you found.
I Have a few ideas like ferrite or plain ironstone with a lustrous interior. Ferrite or ironstone as we all know can be picked up on our pick magnets but if our detector is properly ground balanced will tune out the signal.
Also have seen bits of metal radiator heating elements not give any or only weak signals and even gold nuggets that do the same. The nuggets which did that were very spongy and probably acting like coils in having their decay signals all over the place cancelling out signals from other parts of the spongy gold or coil.
As an aside possibly this phenomenon may be related to why we sometimes get "warbling" signals from gold (and other targets), in getting competing signals from different parts of a nugget. ie a large signal (down tone) from the more massive part of a nugget and a small signal (up tone) from the smaller part of the nugget.
Maybe its only me but get frustrated when an item is put up for identification and then after people venture some ideas nothing more is heard or if an identification has been made it has not been shared.
Hope you have enough posts now to allow you to provide a picture of the item so we can provide some better guesses.

 

[Sveto]

I had this interesting thing happened few weeks ago while visiting a friend in Queensland. I dropped a magnetic hook (very strong magnet) onto the driveway and when I picked it, it had quite a lot of pieces of gravel tuck to the magnet. There were the brown ones that I assumed were iron stone but also quite a lot of light gray ones. I wasn't detecting or anything but was very intrigued by this, specially by how many magnetic little pebbles the magnet picked.

 

[XLOOX]

Just to do your head in, there are a STACK of minerals that will stick to a magnet, of which magnetite is just the most common, followed by maghemite. Most contain iron.

Maghemite is often brown but can be grey black like magnetite. It is pretty easy to tell the diff though even if both rocks are grey/black - if you scrape the rock on something harder - like a file or hard sharpening stone, the magnetite will streak grey and the maghemite will streak brown.

ANY of the 8 minerals in the list with "Ferrimagnetic" in the 3rd column will stick to a strong rare earth magnet but most bits you find wont be detected by a PI detector, it depends on the size, structure and alignment of the microscopic crystal magnety bits in an individual piece.