looks like coral. horn coral

Thanks for your reply, Jeff! I also sent the photos to my uncle, who was a geology major in college. His reply: “That looks ancient weathered coral. It was much warmer water 65 million years ago. Cool. Hard to tell, though.”

It kind of looks like a sea urchin too, with the heart shape. Does it have a hole in the upper other side?

Thanks for your reply, Lisa. I’ve added a third photo of the area I think you’re referencing. There are 4 distinct, small holes along this edge plus 1 or 2 more that appear to have filled in with crystals (please excuse the layman’s terms). I’m curious for any additional thoughts on this now that you’ve proposed an alternate ID.

if there was a certain marking it would be sea urchin mouth.