Magnesium carbonate hydrates have various morphologies. They are generally classified into crystalline and amorphous forms. The structure of magnesium carbonate hydrates depends on the concentration of carbon dioxide (CO2), temperature and pH value. However, investigations are still necessary to understand the conditions of the formation of magnesium carbonate hydrates.
Amorphous magnesium carbonate hydrates can be formed by mixing soluble magnesium salt with sodium bicarbonate. Then, the mixture is stirred at high speed for a period of two hours. During this time, the resulting suspension becomes white and a three-dimensional hydrogen-bonding network is formed.
Synchrotron X-ray scattering experiments were performed to study the structural changes of amorphous magnesium carbonate. It was found that the medium range structural order of the AMC is unchanged.
However, the symmetry of the MgO-CO2-H2O system has been altered. In the amorphous form, the molecule’s O6 atom is located on the mirror plane, while the atoms C1 and O5 are in the (001) plane. This resulted in the formation of a symmetrical three-dimensional hydrogen-bonding network.
Among the crystalline magnesium carbonate hydrates, the Mg5(CO3)4(OH)2*4H2O is the most common form. Besides, the other four hydrates, namely the heavy, light, pentahydrate and monoclinic, also have their own unique morphologies.
Calcification usually occurs as hard, white nodules. These calcifications can be seen in hyperarid and andisol soils. Calcium pyrophosphate dihydrate crystals can accumulate in connective tissues and joints.
Various double salts of magnesium carbonate have been obtained. Ammonium ion is involved in the synthesis of the double salts.