When the rock is blasted it forms nice columns, like these. The Giants Causeway in Northern Ireland have similar basalt columns, but in a seaside setting.

They are surprisingly heavy for their size, and are really hard rocks. These are crushed and used to make super concrete. This is the concrete for really big structures, like the World Square building and Anzac Bridge in Sydney.

We were allowed to take some home, and our columns sit happily in our garden at home.