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Rock Forming Minerals
Published in Aurèle Parriaux, Geology, 2018
Anhydrite is often associated with gypsum in sedimentary deposits. Anhydrite forms from the loss of a water molecule from gypsum as pressure and temperatures increase after gypsum is buried. The principal characteristic of anhydrite is that it can be retransformed into gypsum by hydration, accompanied by a significant increase in volume. This can create problems in underground constructions (Chap. 13).
Rock Forming Minerals
Published in Aurèle Parriaux, Geology, 2018
Anhydrite is often associated with gypsum in sedimentary deposits. Anhydrite forms from the loss of a water molecule from gypsum as pressure and temperatures increase after gypsum is buried. The principal characteristic of anhydrite is that it can be retransformed into gypsum by hydration, accompanied by a significant increase in volume. This can create problems in underground constructions (Chapt. 13).
Industrial Minerals
Published in Earle A. Ripley, E. Robert Redmann, Adèle A. Crowder, Tara C. Ariano, Catherine A. Corrigan, Robert J. Farmer, L. Moira Jackson, Environmental Effects of Mining, 2018
A. Ripley Earle, Robert E. Redmann, Adèle A. Crowder, Tara C. Ariano, Catherine A. Corrigan, Robert J. Farmer, Earle A. Ripley, E. Robert Redmann, Adèle A. Crowder, Tara C. Ariano, Catherine A. Corrigan, Robert J. Farmer, L. Moira Jackson
Gypsum is a hydrous calcium sulphate (CaSO4·2H2O). When calcined, it releases three-quarters of its water to form plaster of paris. This can be moulded as a hard plaster and is used in paint, paper, wallboard, plastics, and joint compounds. Anhydrite is the naturally occurring anhydrous form of gypsum; it is used in cement manufacture and as a crop fertilizer.
The origin and alteration of calcite cement in tight sandstones of the Jurassic Shishugou Group, Fukang Sag, Junggar Basin, NW China: implications for fluid–rock interactions and porosity evolution
Published in Australian Journal of Earth Sciences, 2018
L. Luo, X. Gao, W. Meng, X. Tan, H. Shao, C. Xiao
Anhydrite generally occurs at the middle diagenetic stage, and may have originated from the dehydration of early gypsum, dissolution and reprecipitation, supersaturation of CaSO4 or from hydrothermal systems (Dworkin & Land, 1994; Shao et al., 2017). If the anhydrite, which occurs as poikilotopic, pore-filling masses or isolated, partial grain replacements, were formed by the dehydration of gypsum during the burial process (Figure 6g, h), gypsum must be precipitated in a relatively acidic diagenetic environment at an early diagenetic stage and form as poikilotopic, pore-filling masses. However, the diagenetic environment was nearly alkaline at early diagenetic stage (Figure 12) and some anhydrite occurs as isolated and partial grain replacements that may be related to the late dissolution of grains and calcite cement (Figure 6g, h) so dehydration of early gypsum was not the main source of anhydrite cements. Poikilotopic, pore-filling anhydrite is hard to precipitate from supersaturation of CaSO4 during burial processes. The geological environment and petrological characteristics show no evidence for hydrothermal activity during the burial process.
From phase diagram to the design of strontium-containing carrier
Published in Journal of Asian Ceramic Societies, 2020
Ying-Cen Chen, Pei-Yi Hsu, W. Tuan, Po-Liang Lai
The crystal water of calcium sulfate hemihydrate was removed during the heating stage to afford anhydrite as the final form for calcium sulfate. The resulting phase analysis was conducted by X-ray powder diffraction (XRD) using a synchrotron X-ray source (Hsinchu, Taiwan). Scanning electron microscopy (SEM) images were recorded to observe the microstructure of the specimens after heat treatment.