It's an oak gall.

https://en.wikipedia.org/wiki/Oak_apple

Jay, that’s fascinating. I have actually saved ( in vintage jars) a few galls I have collected over the years, but they’re all buff, tan colors — I never realized they could be in such amazing colors, according to wasp species.

Huh, interesting. I never saw one this color, and I always thought they kind of grew on a branch, kind of around the branch. Thanks Jay

:)

Dee

You're welcome Dee! They do grow on the tree and often fall off. It's a nice color. It looks delicious but I wouldn't try eating it.

Here is some additional info - nature is so cool!

https://www.backyardnature.net/n/x/plumgall.htm

Very cool.

Interesting - thanks for the link. I didn't know that different wasps lay their eggs on different parts of the oak. I've seen both the twig and leaf galls on my live oak and others, but not sure about acorn galls.