Crystal growth of gypsum produced by decomposition of Kola rock phosphate with sulfuric acid has been discussed by statistical analysis.
The crystal from Kola phosphate grew in larger size than those from Cosia, Florida and Morocco phosphates. Larger crystal with plate form grew by the decomposition at 90°C than that below 80°C.
Regarding these causes it was supposed that the Kola phosphate produces calcium sulfate hemihydrate at lower temperatures than the another phosphate rocks, and this hemihydrate converts into dihydrate slowly. The power of the Kola phosphate of -200+230 Tyler mesh produced larger crystal than the coaser or finer powder. The finer produced needle crystal probably owing to higher hydration velocity of the hemihydrate produced.

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Hexagonal plate-like natural clay mineral, such as kaolinite Al₂O₃·2SiO₂ 2 H₂O, is usually available as a filler material in paper making. Particles analogous to kaolinite are found in the hydration of portland cement. These are resulted from the interaction of calcium aluminate phase and various salts and have a general formula 3 CaO·Al₂O₃ Ca (X, Y₂) ·WH₂O. Ettringite which is closely related to these compounds in the compositions has been useing as a filler in paper making, which is alternatively called “Satin White”.
In present paper, the authors show the preparations and the properties of these compounds containing SO₄^-as X and OH^-, NO₃^-, Cl^- as Y. The preparations are undertaken by stirring the aqueous suspensions containing equi-molar mixture corresponded to the compositions. The higher the reaction temperatures under 100°C, the higher the yield of compounds.
However, the yield of 3 CaO·Al₂O₃·Ca (OH) ₂·12H₂O is less as the reaction temperature increases, because the compound tends to transform to a cubic hexahydrate 3 CaO·Al₂O₃·6H₂O in higher temperatures. Electron microscopic observation showed that the compounds got in present studies are hexagonal plate-like crystals except for the cubic product and are 1-20μ in size.
No change in morphology of these compounds is observed in air and in an atmosphere with 30% relative humidity and 100% CO₂, however, in an atmosphere with 100% relative humidity and 100% CO₂, the markedly changes are observed in their morphologyies and their chemical compositions which are resulted from μ-CaCO₃ formation.

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