Gypsum Crystals Formed by the Anhydrite–Gypsum Transformation at Low Temperatures: Implications for the Formation of the Geode of Pulpí
Determining the mechanisms of the formation of giant crystals is a challenging subject. Gypsum, calcium sulfate dihydrate (CaSO4·2H2O), is known to form crystals larger than one meter in several locations worldwide. These selenite crystals grow at different temperatures, either in sedimentary or hyd...
| Autores: | , , , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2024 |
| País: | España |
| Institución: | Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya) |
| Repositorio: | Recercat. Dipósit de la Recerca de Catalunya |
| OAI Identifier: | oai:recercat.cat:2445/226113 |
| Acceso en línea: | https://hdl.handle.net/2445/226113 |
| Access Level: | acceso abierto |
| Palabra clave: | Mineralogia Cristal·lografia Geoquímica Mineralogy Crystallography Geochemistry |
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oai:recercat.cat:2445/226113 |
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España |
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Gypsum Crystals Formed by the Anhydrite–Gypsum Transformation at Low Temperatures: Implications for the Formation of the Geode of Pulpí Cotellucci, Andrea Garcia-Ruiz, Juan-Manuel Otálora, Fermín Canals i Sabaté, Àngels Bruno, Marco Wehrung, Quentin Pellegrino, Luca Aquilano, Dino Pastero, Linda Mineralogia Cristal·lografia Geoquímica Mineralogy Crystallography Geochemistry Determining the mechanisms of the formation of giant crystals is a challenging subject. Gypsum, calcium sulfate dihydrate (CaSO4·2H2O), is known to form crystals larger than one meter in several locations worldwide. These selenite crystals grow at different temperatures, either in sedimentary or hydrothermal systems. The famous selenite crystals of the geode of Pulpí (Almería, Spain) are known to have grown at a temperature T = 20 ± 5 ◦C and have been proposed to form in a subaqueous environment by a self-feeding mechanism triggered by anhydrite dissolution and the ripening of microcrystalline gypsum, enhanced by oscillations in temperature. This paper reports the monitored crystallization of gypsum crystals, from anhydrite powder dissolution, inside airtight evaporation-free reactors under oscillating low temperatures (15 ◦C < T < 25 ◦C). These crystals are clearly smaller than the ones in the Pulpí mine but exhibit similar habits (i.e., single blocky crystals and twins following the 100 twinning law). The growth rate of gypsum single crystals has been measured to be between 3.8 and 35.3 μm/day. Noteworthy, we document the occurrence of the 100 contact twinning law of gypsum, which is the most widespread twinning law in natural environments but never univocally reported in laboratory experiments. The selection of the 100 contact twinning law has been correlated to the low supersaturation values obtained in the experiment, where the concentration in these long-duration experiments can be safely assumed to be the equilibrium concentration, i.e., 0.3 (at 25 ◦C) ≤ SI ≤ 0.4 (at 15 ◦C).We discuss the relevance of our experiment for forming the gypsum crystals of Pulpí in the framework of the geological history of Pulpí mineralization. These laboratory model experiments contribute to a deeper understanding of mineral nucleation and growth processes in natural environments. MDPI https://hdl.handle.net/2445/226113 |
| title |
Gypsum Crystals Formed by the Anhydrite–Gypsum Transformation at Low Temperatures: Implications for the Formation of the Geode of Pulpí |
| spellingShingle |
Gypsum Crystals Formed by the Anhydrite–Gypsum Transformation at Low Temperatures: Implications for the Formation of the Geode of Pulpí Cotellucci, Andrea Mineralogia Cristal·lografia Geoquímica Mineralogy Crystallography Geochemistry |
| title_short |
Gypsum Crystals Formed by the Anhydrite–Gypsum Transformation at Low Temperatures: Implications for the Formation of the Geode of Pulpí |
| title_full |
Gypsum Crystals Formed by the Anhydrite–Gypsum Transformation at Low Temperatures: Implications for the Formation of the Geode of Pulpí |
| title_fullStr |
Gypsum Crystals Formed by the Anhydrite–Gypsum Transformation at Low Temperatures: Implications for the Formation of the Geode of Pulpí |
| title_full_unstemmed |
Gypsum Crystals Formed by the Anhydrite–Gypsum Transformation at Low Temperatures: Implications for the Formation of the Geode of Pulpí |
| title_sort |
Gypsum Crystals Formed by the Anhydrite–Gypsum Transformation at Low Temperatures: Implications for the Formation of the Geode of Pulpí |
| author |
Cotellucci, Andrea |
| author_facet |
Cotellucci, Andrea Garcia-Ruiz, Juan-Manuel Otálora, Fermín Canals i Sabaté, Àngels Bruno, Marco Wehrung, Quentin Pellegrino, Luca Aquilano, Dino Pastero, Linda |
| author_role |
author |
| author2 |
Garcia-Ruiz, Juan-Manuel Otálora, Fermín Canals i Sabaté, Àngels Bruno, Marco Wehrung, Quentin Pellegrino, Luca Aquilano, Dino Pastero, Linda |
| author2_role |
author author author author author author author author |
| topic |
Mineralogia Cristal·lografia Geoquímica Mineralogy Crystallography Geochemistry |
| topic_facet |
Mineralogia Cristal·lografia Geoquímica Mineralogy Crystallography Geochemistry |
| description |
Determining the mechanisms of the formation of giant crystals is a challenging subject. Gypsum, calcium sulfate dihydrate (CaSO4·2H2O), is known to form crystals larger than one meter in several locations worldwide. These selenite crystals grow at different temperatures, either in sedimentary or hydrothermal systems. The famous selenite crystals of the geode of Pulpí (Almería, Spain) are known to have grown at a temperature T = 20 ± 5 ◦C and have been proposed to form in a subaqueous environment by a self-feeding mechanism triggered by anhydrite dissolution and the ripening of microcrystalline gypsum, enhanced by oscillations in temperature. This paper reports the monitored crystallization of gypsum crystals, from anhydrite powder dissolution, inside airtight evaporation-free reactors under oscillating low temperatures (15 ◦C < T < 25 ◦C). These crystals are clearly smaller than the ones in the Pulpí mine but exhibit similar habits (i.e., single blocky crystals and twins following the 100 twinning law). The growth rate of gypsum single crystals has been measured to be between 3.8 and 35.3 μm/day. Noteworthy, we document the occurrence of the 100 contact twinning law of gypsum, which is the most widespread twinning law in natural environments but never univocally reported in laboratory experiments. The selection of the 100 contact twinning law has been correlated to the low supersaturation values obtained in the experiment, where the concentration in these long-duration experiments can be safely assumed to be the equilibrium concentration, i.e., 0.3 (at 25 ◦C) ≤ SI ≤ 0.4 (at 15 ◦C).We discuss the relevance of our experiment for forming the gypsum crystals of Pulpí in the framework of the geological history of Pulpí mineralization. These laboratory model experiments contribute to a deeper understanding of mineral nucleation and growth processes in natural environments. |
| publishDate |
2024 |
| format |
article |
| status_str |
publishedVersion |
| url |
https://hdl.handle.net/2445/226113 |
| eu_rights_str_mv |
openAccess |
| publisher |
MDPI |
| institution |
Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya) |
| collection |
Recercat. Dipósit de la Recerca de Catalunya |
| reponame_str |
Recercat. Dipósit de la Recerca de Catalunya |
| instname_str |
Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya) |
| _version_ |
1878431873142620160 |
| publishDateSort |
2024 |
| author_browse |
Aquilano, Dino Bruno, Marco Canals i Sabaté, Àngels Cotellucci, Andrea Garcia-Ruiz, Juan-Manuel Otálora, Fermín Pastero, Linda Pellegrino, Luca Wehrung, Quentin |
| publisherStr |
MDPI |
| score |
6,9303427 |