Columnar joints formed in sandstone are in shape similar to the ones in igneous rocks.
But unlike the columnar joints formed in igneous rocks, in sandstones the columnar joints are result of heating and cooling both. During heating, contraction stress may be established that can facilitate the development of columnar jointing during cooling of the rock below their softening point, i.e.,about half the melting point.
Larger columns occur in more massive and thickly bedded sandstones. They contain more glass, and hence have a greater tensile strength resulting in more widely spaced fractures.