What Are the Two Most Common Carbonates?

Calcite

• Calcite, also known as calcium carbonate (CaCO3), is by far the most common mineral in the carbonate family, and indeed one of the most common minerals found on Earth. Calcite is common in soil although not if the soil has a pH value below 5.0. Calcite is the chief ingredient of limestone and also produces oolitic and fossiliferous in sedimentary environments, as well as in shale and sandstones. Calcite is also a common ingredient found in mortars and cement mixes, as well as in limestone and glass production.

Calcite Varieties

• Since calcite is such a common mineral, constituting 4 percent of the Earth's crust according to Galleries, it is also found in nature in abundant varieties of crystal forms. One of the most well-known varieties is the scalenohedron, also known as the "Dogtooth Spar." This crystalline form is commonly found in a dipyramind shape, its sharp point resembling a canine tooth, hence the nickname. Calcite is also often found in the form of what is called the Mexican onyx, used commonly as ornamental figurines, as well as in bookends, vases, plates, statues and more. The Mexican, unlike the quartz onyx, comes in a wide variety of colors: black, white, tan, yellow and red.

Dolomite

• Dolomite (CaMg(CO3)2), or calcium magnesium carbonate, is the second most common carbonate although not nearly as ubiquitous as calcite. Like calcite, dolomite also occurs naturally in soils, mainly found from a parent source, dolostone, common in many rocks in many different climates on Earth. Dolomite is also a common ingredient in limestone and thus contributes to commercial uses. Dolomite occurs as a transparent or opaque substance yet can also be found in many other colors, including white, yellow, pink and brown.

Other Common Carbonates

• Azurite (Cu3(CO3)2(OH)2) is a carbonate mineral form of metallic copper commonly found in nature as a blue color. Malachite (Cu2(CO3)(OH)2), also found in metallic copper and often found together with azurite, is characterized by a green color. Magnesite (MgCO3), the carbonate mineral of magnesium, is commonly found with quartz and used for gems in jewelry.