The Christmas Rock.

"This is the same Christmas rock I had when I was a kid; it's an heirloom that's been in our family for generations."
Manny to Peaches[src]

The Christmas Rock was a large chunk of granite that was used to celebrate Christmas.


A huge, red boulder, Christmas Rocks were a tradition for mammoths around Christmas: the rock was set out in plain sight on Christmas Eve so that Santa Claus might see it and bring the mammoths that had set it out presents. Manny gave his old Christmas rock to Peaches. When Sid was showing Manny how he'd decorate a tree, he put the star on but fell off the top which sent the star flying. It hit the rock, shattering it.