How to Make Stone in Little Alchemy 2

Stone is often used to create various combinations in Little Alchemy 2. It can be used to make Blade, Boulder, Brick, Castle, Chimney, Clay, Fossil, Gravestone, Moon, Moss, and Pyramid. Stone is necessary to combine most of the complicated element, although Stone is easy to be combined. See the detailed instructions below.

Air + Air = Pressure
Earth + Pressure = Stone