HELP REQUEST connoisseurs. What is it? Is it a rock, a fossilized egg, a fossilized fruit?

[CarlArthurKing]

Hello everyone. I found this piece in one of my journeys to the Cali mountains (Farallones hillsides), in my country Colombia, South America.

Please let me know what do you think it is.

I thought it was a fossilized fruit, but it seems to have like a shell or so.

I also want to know, -no matter what it is-, how can I preserve it the better possible way, so I can keep it safe for years to come.

A big hug for you all.

C.A.King Zapata

[Tidgy's Dad]

That would seem to me to be a concretion. 

[Rockwood]

I spent some time with a big stainless steel nut found in the same Texas creek as a nearly identical concretion, trying to break it open. So I doubt preservation will be a problem.

 As is often, but not always, the case there were a few indistinct shell fossils in it.