Wondrous Item, rare
While touching this 5-pound stone to the ground, you can take a Magic action to summon an Earth Elemental. The elemental appears in an unoccupied space you choose within 30 feet of yourself, obeys your commands, and takes its turn immediately after you on your Initiative count. The elemental disappears after 1 hour, when it dies, or when you dismiss it as a Bonus Action. The stone can’t be used this way again until the next dawn.
This seems like it'll be really fun to use now that it's been buffed. Can't wait to summon an elemental from the earth to slam people around and burrow into the ground.
Would this work in a dungeon, or does “ground” mean unworked earth or stone?
My call would be stone or dirt directly touching the earth. Wooden walkway over dirt/stone? No, stone tiles over rock in a dungeon? Sure. Second floor in a keep or building? Nope.
Check with your DM of course.