The Dolomite Group is composed of minerals with an unusual trigonal bar 3 symmetry. The structure of the Dolomite Group is taken from the Calcite Group structure. The Calcite Group structure is layered with alternating carbonate layers and metal ion layers. This ordered layering of different or nonequivalent ions causes a loss of the two fold rotational axes and mirror planes that are present in the Calcite Group structure. The loss of symmetry allows only simple crystal forms to be used by the Dolomite Group minerals, mostly rhombohedrons.
Dolomite is a very common mineral and ankerite is much more scarce.
The other members are considered rare to very rare. The rarity of the members of this group can be tied to the closeness in radius of the A and B ions. If the A and B ions are close in radius, then they tend to not segregate as easily into the separate A and B layers, which is required to form this structure and therefore these minerals. The borate minerals nordenskoldine and tusionite are isostructural with the Dolomite Group minerals.