is an anhydrous carbonate mineral composed of calcium magnesium
carbonate, ideally CaMg(CO3)2. The word dolomite is also used to
describe the sedimentary carbonate rock, which is composed predominantly
of the mineral dolomite (also known as dolostone).
dolomite crystallizes in the trigonal-rhombohedral system. It forms
white, tan, gray, or pink crystals. Dolomite is a double carbonate,
having an alternating structural arrangement of calcium and magnesium
ions. It does not rapidly dissolve or effervesce (fizz) in dilute
hydrochloric acid as calcite does. Crystal twinning is common.
Solid solution exists between dolomite, the iron-dominant ankerite and
the manganese-dominant kutnohorite. Small amounts of iron in the
structure give the crystals a yellow to brown tint. Manganese
substitutes in the structure also up to about three percent MnO. A high
manganese content gives the crystals a rosy pink color. Lead, zinc, and
cobalt also substitute in the structure for magnesium. The mineral
dolomite is closely related to huntite Mg3Ca(CO3)4.
Because dolomite can be dissolved by slightly acidic water, areas of
dolomite are important as aquifers and contribute to karst terrain