Dolomite is a major carbonate mineral, being an intermediate member between calcite and magnesite. Despite this, the substitution between calcium and magnesium is only partial, so that calcite and magnesite do not constitute extremes of a complete solid solution. The mineral is recognized by its rhombohedral habit and cleavage and its hardness (3.5-4 on the Mohs scale), differentiating from the former by presenting less effervescence to hydrochloric acid, and may be colorless, white, gray, green, brown or black. In coarse-grained cleavable masses, sometimes in fine-grained or compact masses.