Clay

Clay is a block usually found near or in bodies of water. It is commonly found along beaches or shores. When mined, 4 clay balls will drop; those can be used to craft clay blocks again, or can be smelted into bricks.

Breaking
Clay blocks can be mined with any item or by hand, but shovels are quickest. Destroying a clay block yields 4 clay balls.

World generation
Clay can be found in or around most bodies of water in the form of blobs.