From Kirbypedia

English Name:	Unknown
Japanese Name:	重いブロック Omoi Burokku Heavy Block
First Game:	Kirby & the Amazing Mirror
Type:	Obstacle

An item in the Kirby games.

A variation on the ubiquitous Star Block that adds a new level of challenge. Made of super dense gray stone, these blocks are impossible to inhale or destroy. Kirby can only use his inhale to slowly move them out of his way, or somehow shake the ground using abilities like Hammer or Burning.

They come in two sizes. The regular sized ones are the same size as regular Star Blocks, and can be dealt with by Kirby alone. The second type is many times larger. They have so far only appeared in Amazing Mirror, where Kirby would need to call for help in order to move them.

Items:

Power-Ups: Warp Star - 1UP - Maxim Tomato - Pep Brew - Candy - Mint Leaf Spicy Food - Mike - Cell Phone - Food - Switch - Air Ride Machine Treasure Chest - Misc. Items

Obstacles: Star Block - Bomb Block - Heave-Ho Block- Hard Block Dream Course Obstacles - Tilt 'n' Tumble Obstacles

Final Weapons: Star Rod - Love-Love Stick - Rainbow Sword Master - Triple Star - Block