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REVIEW & ANALYSIS

Gypsum, a Tricky Material

^a Estación Experimental de Aula Dei CSIC, PO Box 13034, 50080 Zaragoza, Spain
^b Universidad de Extremadura, 10600 Plasencia, Spain
^c Plant and Soil Science Department, Texas Tech University, Lubbock, TX 79409

^* Corresponding author (jhi{at}eead.csic.es).

The familiarity of mankind with gypsum and its simple composition are in contrast with the frequent mistakes reported for its behavior and role in nature. Gypsum has been studied as a raw material, as a rock constituent, as an indicator of geological and archaeological conditions, and from other points of view. However, its role in Earth surface processes, its relationship to life through calcium in the equilibrium of carbonates and its structural water molecules, seems overlooked. Moreover, errors of gypsum formulation, analysis, and behavior obscure some of its roles within nature. The semi-solubility of gypsum explains its actions in many soils. The softness, fragility, and crystal water of gypsum are often not considered. Routinely drying at 105°C and pulverizing samples for lab analyses casts suspicion on all analytical results because gypsum becomes anhydrite and/or bassanite at this temperature. Specific physicochemical models are needed to predict the behavior of soils mainly composed of gypsum.