Basalt is an alkaline, igneous rock of volcanic origin. It is composed of a mixture of iron and magnesium silicates with pyroxene and feldspar, usually also with olivine. Basalt is formed by the cooling of flowing magma on the earth's surface or in the sea and is considered the rock with the largest distribution worldwide.
Appearance: Typical dark shade, dark grey to black, also blue and grey-blue. The structure of basalt is always very fine-grained and dense. The direction of flow of the lava mass is often recognizable in the rock.
Properties: Basalt weathers extremely slowly, is frost-resistant and resistant to de-icing salt. Due to its tendency to become slippery when abrasion and slippery when wet, it is hardly used for public road surfaces today.
Use in construction: terrace/garden slabs, gravel and chippings, component of mineral wool.
Examples of basalt varieties: London basalt lava, Mayen basalt lava.
Source: bauwion
