As marble it is more compact and crystalline. Some marble metamorphosed from dolomite, composed of calcium magnesium carbonate. Onyx marbles did not metamorphose from limestone but are calcium carbonate deposited by water. Verd antiques are marbles made up chiefly of serpentine, a hydrous magnesium silicate. Commercially, any rock containing calcium carbonate that can be polished is called marble.
Pure marble is white.
It varies widely in color, however, from white to black through almost every shade of the spectrum. Impurities such as silica, iron oxides, and graphite give marble its color and characteristic rich veining and clouding. In texture it has a wide range from fine to coarse, and it takes a good polish. Marble is easily carved for statues. Impervious to moisture and fire resistant, it is ideal for monuments and fireproof buildings.