When lava pours out and cools slowly over time, a curious geometric pattern emerges: long columns of hexagonal basalt rock, sometimes forming cliffs that stretch hundreds of feet into the air. These igneous rock formations can be found all around the world, from Ireland to Israel to Japan to California, each adding a fascinating structure to the landscapes and waterscapes in which they are settled.
It's amazing to think that a violent eruption of lava however many thousands of years ago could result in something so symmetrical. It is the nature of basaltic lava cooling that allows this to happen: this lava is hotter and moves faster than 
other kinds. As it cools from the bottom up and from the center outward, long fractures form columns that at times take on astoundingly clear-cut hexagons. The whole process is called columnar jointing.
These columns form in vast bunches and are often found near sources of water, along an island's coast or in the middle of a river or stream. Create your piece of the rock here.