Bone Block

On current versions there is no block item to collect. The Bone Wand paints it directly out of the Bones in your inventory, and breaking a placed one gives bones back rather than blocks. Building with it is a closed loop through the wand, which is more convenient than it sounds: there is nothing to haul, and you never end up with an awkward half stack.

Walls and furniture in the same style are made from raw bones at a Bone Welder, not from the block. Very old console and 3DS worlds behave differently and can leave you holding block items with no way to convert them back, which is the one case where the modern loop is clearly the better design.