Please help ID this rock I found metal detecting on the beach!!

[Swhetstone]

Hey everyone. I haven't had any luck finding out what kind of rock this is. It beeps with my metal detector and is not magnetic. At least i can't feel any draw with a rare earth magnet. I just broke a piece off with a hammer and chisel and it was hard even trying to split it on a grove. Some yellowish color on the inside. Thanks in advance for any input!!

 

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[Stegner]

looks to be of even thickness...like its just a well-decayed piece of iron.

 

[rock]

Might be a natural mix of iron ore.

 

[Jeff H]

Possibly graphite. Does it leave a mark like a pencil?

 

[Swhetstone]

No when i rub it on a piece of paper or business card it leaves no marks

 

[dennco2000]

Looks like a type of schist, there are a lot of types. I think you have an ore with mica shist flakes maybe.
Look here.

http://skywalker.cochise.edu/wellerr/rocks/mtrx/schistL.htm

 

[dieselram94]

I found a similar "rock" on a beach in Scarborough Maine recently. I just stated a new thread on it a little while ago. Mine is defiantly blacker though but sounds off on detector but magnet does not stick as well. Leaves no marks either.

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