Figure 1
(a) Crystallographic structure of calcium sulfate hemihydrate (Ballirano et al., 2001) along the c direction and SEM image of a typical α-hemihydrate crystal. (b) Crystallographic structure of calcium sulfate dihydrate (Boeyens & Ichharam, 2002) along the c direction and SEM image of an aggregate of gypsum crystals of different sizes and shapes. The SEM images have been taken with a VEGA3 TESCAN scanning electron microscope with a voltage of 16 kV. Legend: blue balls – Ca atoms; yellow balls – S atoms; red balls – O atoms; white balls – water molecules. |