Photo from Heart of Stone Studio at http://www.heartofstonestudio.com/Wind-Cloud-Agate-Druzy-ZN536

Photo from http://www.northlincolnagatesociety.org/

Cloud agates look like they contain clouds. They can have a gray or transparent matrix and the inclusions are usually white and foggy to look like clouds.  The one on the left has a bit of a drusy effect which makes it look like a puffy cumulus cloud.  The cloud agate on the right has a blue “cloud” inside.  The North Lincoln Agate Society has given its friend some googly eyes.