Carbonates are salts that are formed by the reaction of carbonic acid with metals or organic compounds. They are generally insoluble in water at standard temperature and pressure.

Calcium carbonate is the most common of all carbonates. It is mainly obtained by the chemical process of calcination of limestone. This process results in the breakdown of calcium oxide, which produces carbon dioxide. The mineral then forms the main component of limestone. Moreover, calcium carbonate is used in the manufacture of cement, ceramics, and glass.

Other carbonates are found in the Earth’s mantle and in sedimentary rock. They are used in the manufacturing of soap, detergent, and glass. Also, they are commonly used in drug development. Some of them are also used in the production of rat poison, fireworks, and chalk.

Carbonates are subject to increasing pressure as they sink down through the Earth’s subduction slabs. For this reason, determining the influence of pressure on their stability is important for geophysics.

BaCa(CO3)2 barytocalcite is the most compressible divalent metal carbonate. Powder XRD measurements of this mineral demonstrate a transition between 4.4 and 5.7 GPa. However, further experiments are necessary to determine the thermodynamic crossovers of other carbonate systems.

In the high-pressure (HP) phase, Ba atoms occupy the space between six carbonate groups. As a result, the arrangement of cations in this phase is very different from that in calcite and paralstonite. Moreover, the HP phase has four different orientations.

Another carbonate mineral is aurichalcite. Aurichalcite is composed of zinc and copper ions. A hydroxyl radical is required for the formation of this complex mineral.

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