Dolomite is mineral whose formula is :

The formula of Dolomite is  $\mathrm{CaMg}{\left({\mathrm{CO}}_3\right)}_2$and ${\mathrm{CaCO}}_3\cdot {\mathrm{MgCO}}_3$ .

A typical mineral that forms rocks is dolomite. Its chemical formula is $\mathrm{CaMg}{\left({\mathrm{CO}}_3\right)}_2$, which indicates that it is a calcium magnesium carbonate. It is the main constituent of the metamorphic rock known as dolomitic marble as well as the sedimentary rock known as dolostone. Dolomitic limestone is a kind of limestone that contains some dolomite.

a dolomite mineral is known as $\mathrm{CaMg}{\left({\mathrm{CO}}_3\right)}_2$, or calcium magnesium carbonate, which is found in crystals and large beds.

Hence, option D is correct.