Carbonates and nitrates form the fifth class of the Strunz mineral classification. Carbonate minerals are characterized by the carbonate group (CO₃) as an essential structural component, while nitrates contain the nitrate group (NO₃). Nitrate minerals are considerably less common in nature than carbonates.

Among the best-known carbonate minerals are calcite, dolomite, aragonite, siderite, rhodochrosite, cerussite and azurite. The class includes widespread rock-forming minerals, important ore minerals and many highly attractive collector minerals.
Calcite (CaCO₃) is one of the most common carbonate minerals and occurs in a wide variety of geological environments. It is a major component of many sedimentary rocks, but it also forms in hydrothermal veins, cavities, ore deposits and metamorphic rocks. Its great variety of crystal forms and the frequent development of well-formed crystals make calcite especially important for mineral collectors.

Dolomite is significant both as a rock-forming mineral and as a mineral in hydrothermal and sedimentary systems. Aragonite has the same chemical composition as calcite but crystallizes in a different crystal system. Siderite and rhodochrosite are iron- and manganese-bearing carbonates respectively, while cerussite is an important secondary lead mineral in the oxidation zones of lead deposits. Azurite is one of the copper-bearing carbonates and is particularly well known for its intense blue colour.

More complex carbonates such as parisite-(Ce) demonstrate the considerable chemical and structural diversity of this mineral class. Such minerals can contain rare-earth elements and may occur in specialized hydrothermal or igneous systems.

Carbonates form through a wide range of geological processes. They occur in sedimentary environments, hydrothermal mineralization, metamorphic rocks, weathering zones and oxidation zones. As a result, carbonate minerals are among the most geologically and economically important mineral groups.

The Mineralien Weltweit range includes various carbonate minerals, including calcite, dolomite, azurite, parisite-(Ce), rhodochrosite, aragonite, cerussite and siderite. Each collector specimen is documented with precise locality information, dimensions, weight and original photographs.