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...

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Autores: Cotellucci, Andrea, Garcia-Ruiz, Juan-Manuel, Otálora, Fermín, Canals i Sabaté, Àngels, Bruno, Marco, Wehrung, Quentin, Pellegrino, Luca, Aquilano, Dino, Pastero, Linda
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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spelling Gypsum Crystals Formed by the Anhydrite–Gypsum Transformation at Low Temperatures: Implications for the Formation of the Geode of PulpíCotellucci, AndreaGarcia-Ruiz, Juan-ManuelOtálora, FermínCanals i Sabaté, ÀngelsBruno, MarcoWehrung, QuentinPellegrino, LucaAquilano, DinoPastero, LindaMineralogiaCristal·lografiaGeoquímicaMineralogyCrystallographyGeochemistryDetermining 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.MDPI2026202620242026info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersion8 p.application/pdfhttps://hdl.handle.net/2445/226113Articles publicats en revistes (Mineralogia, Petrologia i Geologia Aplicada)reponame:Recercat. Dipósit de la Recerca de Catalunyainstname:Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya)InglésReproducció del document publicat a: https://doi.org/10.3390/min14111074Minerals, 2024, vol. 14, num.11https://doi.org/10.3390/min14111074cc-by (c) Cotellucci, A. et al., 2024http://creativecommons.org/licenses/by/4.0/info:eu-repo/semantics/openAccessoai:recercat.cat:2445/2261132026-05-29T05:05:01Z
dc.title.none.fl_str_mv Gypsum Crystals Formed by the Anhydrite–Gypsum Transformation at Low Temperatures: Implications for the Formation of the Geode of Pulpí
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
dc.creator.none.fl_str_mv Cotellucci, Andrea
Garcia-Ruiz, Juan-Manuel
Otálora, Fermín
Canals i Sabaté, Àngels
Bruno, Marco
Wehrung, Quentin
Pellegrino, Luca
Aquilano, Dino
Pastero, Linda
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
dc.subject.none.fl_str_mv Mineralogia
Cristal·lografia
Geoquímica
Mineralogy
Crystallography
Geochemistry
topic 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
dc.date.none.fl_str_mv 2024
2026
2026
2026
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv https://hdl.handle.net/2445/226113
url https://hdl.handle.net/2445/226113
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv Reproducció del document publicat a: https://doi.org/10.3390/min14111074
Minerals, 2024, vol. 14, num.11
https://doi.org/10.3390/min14111074
dc.rights.none.fl_str_mv cc-by (c) Cotellucci, A. et al., 2024
http://creativecommons.org/licenses/by/4.0/
info:eu-repo/semantics/openAccess
rights_invalid_str_mv cc-by (c) Cotellucci, A. et al., 2024
http://creativecommons.org/licenses/by/4.0/
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv 8 p.
application/pdf
dc.publisher.none.fl_str_mv MDPI
publisher.none.fl_str_mv MDPI
dc.source.none.fl_str_mv Articles publicats en revistes (Mineralogia, Petrologia i Geologia Aplicada)
reponame:Recercat. Dipósit de la Recerca de Catalunya
instname:Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya)
instname_str Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya)
reponame_str Recercat. Dipósit de la Recerca de Catalunya
collection Recercat. Dipósit de la Recerca de Catalunya
repository.name.fl_str_mv
repository.mail.fl_str_mv
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score 15.812429

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