Brown Rocks are obstacles in Mario & Luigi: Superstar Saga. There found throughout the Beanbean Kingdom. They can be demolished by any hammer. They are first introduced at Hoohoo Mountain, in the home of the Hammerhead Bros, whom forge a hammer outta Hoohoo Block for Mario & Luigi. Brown Rocks are mostly used early on, serving as a tutorial for using hammers.
In Mario & Luigi: Superstar Saga + Bowser's Minions, they appeared as cracked gray rocks.