Details
| Original language | English |
|---|---|
| Pages (from-to) | 289-299 |
| Number of pages | 11 |
| Journal | European journal of mineralogy |
| Volume | 31 |
| Issue number | 2 |
| Early online date | 1 Apr 2019 |
| Publication status | Published - 7 Jun 2019 |
| Externally published | Yes |
Abstract
The mineral replacement of gypsum (CaSO 4.2H 2O) by baryte (BaSO 4) is relevant to technological and industrial applications, including its use as a plaster or stone consolidant in cultural heritage conservation. In the present study, we provide experimental evidence suggesting that, during the interaction of gypsum cleavage surfaces with barium-bearing solutions, a pseudomorphic replacement takes place and results in the formation of a crystallographically oriented baryte layer. This mineral replacement process is favoured by the porosity generated, due to the differences in molar volume and solubility between parent and product sulfate phases, allowing the progress of the reaction. The homogeneous micrometre-sized layer of baryte occurs most likely via a fluid-mediated interface-coupled dissolution–precipitation mechanism. A certain degree of crystallographic control on the polycrystalline BaSO 4 product layer by the structure of the parent substrate (gypsum) is confirmed by electron microscopy observations and X-ray diffraction analyses. The structural control exerted by the cleavage gypsum surface on the baryte layer can be defined by the epitactic relationship: Gyp (010) || Bar (010). The formation of baryte increases with reaction time until passivation occurs at the replacement interface, probably due to a decreased porosity and loss of connectivity that thereby prevents further reaction. The investigation of these processes occurring on freshly cleaved single crystals of gypsum were complemented by studying the replacement of polycrystalline gypsum cubes, showing a homogeneous baryte surface layer on the sample. The results of this study thus offer interesting insights into the application of the replacement of gypsum by baryte as a conservation method for gypsum sculptures and plasterwork, increasing their resistance against water and humidity while preserving the surface features of the original mineral substrate.
Keywords
- Baryte, Conservation, Epitaxy, Gypsum, Pseudomorphic replacement
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
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In: European journal of mineralogy, Vol. 31, No. 2, 07.06.2019, p. 289-299.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Baryte cohesive layers formed on a (010) gypsum surface by a pseudomorphic replacement
AU - Ruiz-Agudo, Cristina
AU - Álvarez-Lloret, Pedro
AU - Lorenzo, Fulvio Di
AU - Gebauer, Denis
AU - Putnis, Christine V.
N1 - Funding Information: This research was carried out within a Marie Curie initial training network from the European Commission (MINSC ITN 290040). The Deutsche Forschungsgemeinschaft (DFG) supports the research at the University of Münster. CRA and DG thank the SFB1214 and the Zukunftskolleg of the University of Konstanz for support. PAL acknowledges funding from CGL-2016-77138-C2-2P. We would like to also thank the personnel of the “Centro de Instrumentación Científica” (University of Granada) for their support and help with the ESEM, FESEM and 2D-XRD analyses. In addition, we would like to thank the Particle Analysis Center of the University of Konstanz (funded by SFB1214) for XRD measurements. FDL thanks the Spanish Government (grants CGL2015-70642-R, CGL2015-73103-EXP), the University of Granada (“Unidad Científica de Excelencia” UCE-PP2016-05) and the Junta de Andalucía (grants P11-RNM-7550 and Research Group RNM-179). All the authors thank Christian Chopin and Carlos Rodríguez Navarro and the three anonymous reviewers for their insightful comments and effort towards improving this manuscript.
PY - 2019/6/7
Y1 - 2019/6/7
N2 - The mineral replacement of gypsum (CaSO 4.2H 2O) by baryte (BaSO 4) is relevant to technological and industrial applications, including its use as a plaster or stone consolidant in cultural heritage conservation. In the present study, we provide experimental evidence suggesting that, during the interaction of gypsum cleavage surfaces with barium-bearing solutions, a pseudomorphic replacement takes place and results in the formation of a crystallographically oriented baryte layer. This mineral replacement process is favoured by the porosity generated, due to the differences in molar volume and solubility between parent and product sulfate phases, allowing the progress of the reaction. The homogeneous micrometre-sized layer of baryte occurs most likely via a fluid-mediated interface-coupled dissolution–precipitation mechanism. A certain degree of crystallographic control on the polycrystalline BaSO 4 product layer by the structure of the parent substrate (gypsum) is confirmed by electron microscopy observations and X-ray diffraction analyses. The structural control exerted by the cleavage gypsum surface on the baryte layer can be defined by the epitactic relationship: Gyp (010) || Bar (010). The formation of baryte increases with reaction time until passivation occurs at the replacement interface, probably due to a decreased porosity and loss of connectivity that thereby prevents further reaction. The investigation of these processes occurring on freshly cleaved single crystals of gypsum were complemented by studying the replacement of polycrystalline gypsum cubes, showing a homogeneous baryte surface layer on the sample. The results of this study thus offer interesting insights into the application of the replacement of gypsum by baryte as a conservation method for gypsum sculptures and plasterwork, increasing their resistance against water and humidity while preserving the surface features of the original mineral substrate.
AB - The mineral replacement of gypsum (CaSO 4.2H 2O) by baryte (BaSO 4) is relevant to technological and industrial applications, including its use as a plaster or stone consolidant in cultural heritage conservation. In the present study, we provide experimental evidence suggesting that, during the interaction of gypsum cleavage surfaces with barium-bearing solutions, a pseudomorphic replacement takes place and results in the formation of a crystallographically oriented baryte layer. This mineral replacement process is favoured by the porosity generated, due to the differences in molar volume and solubility between parent and product sulfate phases, allowing the progress of the reaction. The homogeneous micrometre-sized layer of baryte occurs most likely via a fluid-mediated interface-coupled dissolution–precipitation mechanism. A certain degree of crystallographic control on the polycrystalline BaSO 4 product layer by the structure of the parent substrate (gypsum) is confirmed by electron microscopy observations and X-ray diffraction analyses. The structural control exerted by the cleavage gypsum surface on the baryte layer can be defined by the epitactic relationship: Gyp (010) || Bar (010). The formation of baryte increases with reaction time until passivation occurs at the replacement interface, probably due to a decreased porosity and loss of connectivity that thereby prevents further reaction. The investigation of these processes occurring on freshly cleaved single crystals of gypsum were complemented by studying the replacement of polycrystalline gypsum cubes, showing a homogeneous baryte surface layer on the sample. The results of this study thus offer interesting insights into the application of the replacement of gypsum by baryte as a conservation method for gypsum sculptures and plasterwork, increasing their resistance against water and humidity while preserving the surface features of the original mineral substrate.
KW - Baryte
KW - Conservation
KW - Epitaxy
KW - Gypsum
KW - Pseudomorphic replacement
UR - http://www.scopus.com/inward/record.url?scp=85066890244&partnerID=8YFLogxK
U2 - 10.1127/EJM/2019/0031-2847
DO - 10.1127/EJM/2019/0031-2847
M3 - Article
VL - 31
SP - 289
EP - 299
JO - European journal of mineralogy
JF - European journal of mineralogy
SN - 0935-1221
IS - 2
ER -