Stone Column

Columns hold up the mine's ceiling to prevent cave-ins. Stone columns have a slightly larger radius (11 tiles) than Mine Supports (9 tiles) and are generally more convenient to build in a mine due to being built with stones.
Note: Mined tiles will still show dust animation (see Mining page) when under the radius of the support, to warn of cave-in tiles, but caveins won't occur under support.
Quoted from Loftar
<SuperDaddy> Does it count if the radius is touching part of the tile?
<loftar> Well, to be precise, it needs to touch the exact center of the tile.
This means tiles covered by the column radius just slightly aren't supported.
Caution: Destroying a stone column underground will immediately cause a cave-in to occur, even if all tiles in it's radius are supported by other columns or supports.
==Support Radius==
All tiles marked in blue are safe to mine. Mining a tile outside of the blue area may cause a cave-in. This structure will support mining within a 11 tile radius.
==Notes==
* Added in update "Spit'n'Polish"
* Stone Columns can be built on the surface and in houses too for aesthetics.