What are these stones?

[FAB]

These stone were found in the early 1970's in NJ when an in-ground pool was installed in my backyard. These were both found at the very bottom of the hole which was dug for the pool at a depth of 4 to 9 feet. They are both similar in shape and one seems to be "broken". If these are both just rocks I'd be surprised, but I can live with that. They're still interesting even if they're only rocks. So....I came across this site and thought I'd ask here to see if anyone has seen anything like this before or would have an inkling as to what they could be. An arrowhead was also found in the same backyard at a different point in time.

 

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[Pork King]

are either of them magnetic?

 

[FAB]

No. Neither is magnetic. The largest one fits perfectly into the hand as if it were a tool of some kind.

 

[travelafar]

The one on the bottom looks like a tool Native Americans made to rub hides while being stretched. The top could be part of a fire making kit. They would hold that rock with the indentation with a stick and bow, spinning the stick while pressing down to create a friction fire.