Dolerite

Dolerite is a rock that belongs to the group of igneous rocks. It is a mafic rock that has properties similar to basalt. In North America, the rock is called diabase, while in other English-speaking parts of the world, the term dolerite is preferred. Geologists sometimes use the term "microgabbro" to avoid confusion [2External link].

Dolerite is a holocrystalline subvolcanic rock equivalent to basaltic volcanic rocks or plutonic gabbro. It occurs as dikes (gangue rocks) and sills (stock dikes). Dolerite usually has a fine but visible texture, consisting of euhedral, needle- or rod-shaped plagioclase crystals embedded in a finer matrix of clinopyroxene, typically augite. Other constituents may include olivine, magnetite, ilmenite, and various secondary minerals such as hornblende, biotite, and apatite. The composition of dolerite can only be determined by microscopic examination [2External link].

Dolerite is relatively low in silicon and rich in minerals. It is harder than granite and has a dark color. It is commonly used in the construction industry, especially for paving stones, curbs, masonry units, and as a ballast material. Dolerite also occurs as a natural rock formation, for example in the form of vertical columns, which can occur in alpine regions [2External link].

In terms of geological formation, dolerite is considered to be a type of igneous rock that forms as an intrusion into the Earth's crust. It usually forms in regions of tectonic extension, and dike-like structures may occur radiating from a single volcanic center. A well-known example of a dolerite sill is the Palisades Sill on the Hudson River in the United States. Dolerite also occurs in various parts of the world, such as Scotland, Ireland, England, India, and the island of Curaçao [2External link].

Location of the rock dolerite near the village Schnellbach/Thuringia

Image: Thomas Voigt