Basalt belongs to the group of igneous rocks. Igneous rocks are formed when hot liquid magma (lava) from the depths of the earth, is forced to the surface by volcanic forces and flows like a mudslide directly over the earth's surface, where it cools down and solidifies. Basalt is used in the road and hydraulic engineering in particular, as a result of its favorable mechanical properties.
Basalt as (geological) young volcanic rock, gets a fine-grained structure when cooling down relatively rapid. It is interspersed with small circular hollow vesicles. The color ranges from dark gray via gray-black to dark blue. Basalt is very solid and
can only be poorly split (whereby very irregular fracture surfaces occur).
An impressive basalt formation is located in Northern Ireland (its counterpart in nearby Scotland) This large basalt massif is known as the Giant's Causeway. The basalt columns present there were created about 60 million years ago when lava from the interior of the earth gradually cooled down at the surface. During this phase, cracks were formed (similar to mud in a pond which dries in the sun) These cracks are located not only on the surface, but also at great depths, more or less extended over the entire height of the solidified lava mass. This resulted in columns so typical for basalt. On the surface the columns form a paving-like pattern, of which the basic shape is mainly penta- or hexagonal. However basalt columns with square, octagonal and even triangular cross sections are also found (however the latter very rarely)