CaMgCO

CaMgCO is not a standardized chemical formula. In mineralogical usage, it may appear as an informal shorthand for calcium–magnesium carbonate systems. The term most commonly alludes to the mineral dolomite, whose ideal chemical composition is CaMg(CO3)2. Writing CaMgCO as an abbreviation is potentially ambiguous because the complete carbonate framework comprises two carbonate groups per formula unit.

Dolomite is a rhombohedral carbonate mineral that is part of the calcite group but with ordered layers of calcium and magnesium. In its crystal structure, Ca2+ and Mg2+ alternate along the c-axis with CO3 carbonate groups occupying interlayers. This ordering gives diffraction and physical properties that distinguish dolomite from calcite.

Dolomite forms in marine settings through diagenetic alteration of limestone or direct precipitation from magnesium-rich fluids, and it occurs worldwide in sedimentary rocks. It can weather to dolostone and, when metamorphosed, may yield magnesium-rich rocks. Commercially, dolomite and dolomite rock are quarried as sources of magnesium oxide and magnesium carbonate, and as aggregate and decorative stone.

Key properties include a Mohs hardness of about 3.5–4, a specific gravity around 2.8–2.9, a vitreous luster, and rhombohedral cleavage. Color ranges from white to gray, sometimes with pink or brown hues due to impurities.

The term CaMgCO should be interpreted with caution; the standard formula for the principal mineral is CaMg(CO3)2. See also calcite, dolomite group, carbonate minerals.