A fossil that responds to a metal detector?? ID help needed

[Jolly Mon]

I found this object underwater around what are probably some very old shipwreck artifacts...but the weird thing is that I found it in zero visibility conditions with a metal detector.

I got it home and it reads -8 on my Xterra 70...pure iron. A Garrett Pro -pointer gives a reading over the entire surface area. It is completely non-magnetic, hard as a rock and very heavy for its size. I think it is either a bone fragment or a piece of wood that has become mineralized over many years by being in contact with iron. Any ideas?? Thanks in advance...

 

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[GatorBoy]

looks like a fossilized section of giant tortoise shell. just a high iron content in the ground where it was resting that got transferred to the piece.

 

[Ninjafossils]

looks like a fossilized section of giant tortoise shell. just a high iron content in the ground where it was resting that got transferred to the piece.

Agree that it probably was infiltrated by iron. But it looks more like the outside edge of an unidentifiable bone fragment.

 

[au-artifax]

Agree that it probably was infiltrated by iron. But it looks more like the outside edge of an unidentifiable bone fragment.

Time for chemical analysis;

File off some of the material, also make some aluminum filings.
Blend them together and OUTSIDE/OUTDOORS put a torch to it.
If it burns (it will be upwards of 3000 degrees hot) then that mixture is called thermite and the piece you found is oxidized cast iron from possibly from a steam engine or part of an old anchor. Cast iron when it oxidizes does not flake the way regular steel does when it oxidizes (rusts). In the absence of atmospheric oxigen it retains it's shape somewhat and turns blackish because of all the impurities and carbon. This type of oxidation is slower and relies on the ion exchange in the water, so the piece you have has some age to it. Does your MD distinguish between iron and feric or ferrous oxide materials?

 

[au-artifax]

Another thing it could be is what they call a "sacrificial rod" or part of one. Newer ships or vessels made of more than one type of metal suffer from what is called "galvanic corrosion". To minimize the effect they attatch rods or ingots of metal to the underside of the hull to suffer most of the corrosion which occurs through interaction with both oxygen and chlorides from the water (chlorides only if it is salt water).

Occasionally these rods (which aren't always "rods") will either fall off or break off after they get brittle from the ion exchange.
Hope this helps.

 

[au-artifax]

A third idea judging by the pics is that it looks like slag from the process of smelting iron. Or slag from the coal firebox in a boiler. Or a chunk of lava. Anyways this idea is because part of it looks as if it were molten at some point. Cheers.