Dolomite with Calcite from Midelt, Morocco (new find in 2024!)

Dolomite or bitterspar is a carbonate mineral; calcium-magnesium carbonate with the chemical formula CaMg(CO3)2. Rock that largely consists of this mineral is also called dolomite, to distinguish it the name dolosteen is also used. In its appearance dolomite resembles calcite, but despite the basic carbonate ion it dissolves poorly or not at all in hydrochloric acid. It is not known exactly how the mineral is formed, one possibility is that it occurs in shallow seawater in (sub)tropical areas, but other mechanisms are also possible. Although the rock is usually not formed by sedimentation, it is still considered a sedimentary rock. The mineral owes its name to the 18th century French geologist Déodat de Dolomieu, who discovered this mineral in the mountain range that has since been called the Dolomites after him. The mineral is usually formed secondarily in limestone, where dolomite is formed by the conversion of pure calcium carbonate. Because Mg ions occupy places of Ca ions in the crystal lattice, holes are created in the rock on both atomic and macro scale. This is typical for secondary dolomite. Dolomite is used as a natural stone, but also as a raw material for cement, as a source of magnesium oxide and for the production of fireproof bricks.