Earth and Planetary Sciences ETDs


Pao-Chin Chao

Publication Date



Gypsum and anhydrite have been found extensively in evaporite beds. Gypsum is the low-temperature, hydrous form of calcium sulfate, while anhydrite is the high-temperature, anhydrous form. The temperature of gypsum-anhydrite transition has been fixed, by both solubility measurements and thermodynamic calculations, in the range of 38 to 42°c in pure water; and at lower values with increasing NaCl content in the solutions. However, the precipitation of anhydrite has never been obtained experimentally in its own stability field, gypsum is always metastably formed instead.

Many investigators believe that the primary precipitation of anhydrite from solutions is improbable. It is usually converted from gypsum by the diagenesis due to the effects of burial, anhydrite is always secondary.

The present work is to study the precipitation of calcium sulfate by mixing CaCl2, with Na4SO4 in various ways to evaluate the possibility of direct precipitation of anhydrite.

It has been found that anhydrite can be formed in concentrated CaCl2 solution, or H2SO4 solution, because the kinetics of nucleation is favored by increased super saturation.

Degree Name

Earth and Planetary Sciences

Level of Degree


Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Edgar F. Cruft

Second Committee Member

Albert Masakiyo Kudo

Third Committee Member

Roger Yates Anderson

Fourth Committee Member

Vincent Cooper Kelley



Document Type


Included in

Geology Commons