Actually basalt columns are mainly hexagonal (six-sided)in shape. I've modeled quite a few basalt formations. I usually start with a subdivided grid and add verts and edges to make six sided columns. Then I extrude these at random several times. Then I bevel a few edges and apply a noise modifier to add randomness so they don't look like they are manufactured. Another way would be to use a displacement map or make a terrain using a grayscale prepared in PS, or another image editor. I would be very interested to see if you can come up with a naturalistic result using the surface replicator.