Cast iron or silver?

[klskippy]

So we are extremely new to decting and this may be a dumb question, BUT, we found a large piece of what looks like cast iron buried in about three feet of san where it has no business being. This large "thing" registers as silver om my dectector. Is that normal? What doed silver look like when its been in sand and saltwater for a long time?

 

[Dig Daddy]

Got a picture?

 

[Bigcypresshunter]

test with magnet