CaMg(CO₃)₃

These samples of dolomite are displayed in the Smithsonian Museum of Natural History. Dolomite is a carbonate mineral which contains calcium and magnesium with the composition CaMg(CO₃)₃. This sample is about 15 cm high and originated in Eugui, Navarra, Spain.

This dolomite sample is from Simplon Tunnel, Binnatal, Valais, Switzerland. It measures about 10x7 cm.

Though most commonly white, dolomite can take on a range of colors. This sample of dolomite is labeled as "cobaltian", presumably implying that the color arises from inclusion of a small amount of cobalt. The sample is about 8x8 cm and is from Tsumeb, Namibia.

Impurities and inclusions can have a dramatic effect, as this dark dolomite sample from Pinal County, Arizona shows. The sample is about 11x8 cm. The contrast is heightened by the almost clear 1.5x1.2cm specimen from Lengengach quarry, Imfeld, Binnatal, Valais, Switzerland.

This sample is about 15x18 cm and originated in Guanajuato, Mexico.

This dolomite specimen is from St. Louis, Missouri and has a diameter of about 14 cm.