Vaterite and production method

Process for the preparation of vaterite in which

• a mixture of particles containing a compound selected from the group consisting of calcium oxide and calcium hydroxide is treated in a reaction medium containing an acid salt of an organic amine so as to convert the calcium into soluble salt and so as to obtain a medium, the pH of which -called pH of treatment- has a value higher than 10, while the calcium content of which is between 0.35 and 0.65 mole/litre;
• CO.sub.2 is introduced into the medium subjected to a stirring so that the pH of the medium reaches a pH--called pH of saturation--, the value of which is about 0.83.times.pH of treatment, and CO.sub.2 is introduced in the medium at a rate lower to 50 g CO.sub.2 /hour/litre so as to form substantially spherical vaterite.