On the Real Structure of Gypsum Crystals

Synthesis, Crystal Structure, and Thermal Properties of CaSO4·2H2O Single Crystals

“…Furthermore, the monoclinic structure with the space group I2/a and unit cell parameters of a=5.670(2) Å, b=15.201(2) Å, c=6.533(2) Å, and β=118.36(4)º , has also been reported in several papers (Cole & Lancucki, 1974;Knight et al, 1999;Schofield et al, 1996). The lattice parameters and atomic coordinates in the C2/c structure are related to those in the I2/a structure by a symmetry operation (Follner et al, 2002); thus, these two reported structures are identical. The structure of CaSO 4 • 2H 2 O consists of SO 4 tetrahedra, CaO 8 polyhedra, and weak hydrogen bonds between the nearest-neighbor oxygen atoms of SO 4 tetrahedra and intercalated H 2 O molecules.…”

Achiral Inorganic Gypsum Acts as an Origin of Chirality through Its Enantiotopic Surface in Conjunction with Asymmetric Autocatalysis

“…Gypsum exhibits a perfect enantiotopic cleavage face that easily appears upon slicing of the crystal (Scheme ). The crystal structure of gypsum belongs to the achiral space group C 2/ c . Ideal surface images of gypsum looking along the b and − b axes are shown in Scheme d. It should be noted that the (010) and (0 0) faces of gypsum form enantiotopic faces and cannot be superimposed on each other with two‐dimensional movement.…”

On the Use of Overtone and Combination Bands for the Analysis of the CaSO4—H2O System by Mid-Infrared Reflection Spectroscopy

“…According to the specific literature in the field of painting conservation, few studies have been carried out on calcium sulfate minerals, 1,[4][5][6] as compared to the profuse literature on the CaSO 4 -H 2 O system in geochemical [7][8][9][10] and industrial applications. [11][12][13] In any case, thermogravimetry structural crystallographic studies as well as vibrational spectroscopic techniques (Raman and infrared (IR)) have been demonstrated to be versatile tools in probing structural changes and dehydration processes of the CaSO 4 -H 2 O system through destructive or micro-destructive methods.…”