Jewel Oak Gall Wasp's Gall

Thanks for the help IDing this.

Sent you my best suggestion. Bugguide has lots of information on other pages and images of the gall for you to compare. Oaks have many kinds of galls that are not dangerous to the health of oaks. :)

Thanks for the info! That leaf is an oak leaf.

It looks like a gall. A wasp lays an egg and the leafy or twig responds by making a gall (protective coat for the larvae). To know which kind of wasp/wasps you need to know what leaf or plant to narrow your search.