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Review

Spanish Bentonites: A Review and New Data on Their Geology, Mineralogy, and Crystal Chemistry

1
Department of Mineralogy and Petrology, Complutense University of Madrid, 28040 Madrid, Spain
2
Geosciences Institute (IGEO) Spanish Research Council and Complutense University (CSIC-UCM), 28040 Madrid, Spain
3
Department of Geology, University of Salamanca, 37008 Salamanca, Spain
4
Center for Nuclear Sciences and Technologies (C2TN), Instituto Superior Técnico, University of Lisbon, 2695-066 Bobadela-LRS, Portugal
*
Author to whom correspondence should be addressed.
Minerals 2019, 9(11), 696; https://doi.org/10.3390/min9110696
Received: 3 October 2019 / Revised: 4 November 2019 / Accepted: 5 November 2019 / Published: 11 November 2019
(This article belongs to the Special Issue Special Clays and Their Applications)
A review and a synthesis of the geological, mineralogical, and crystal chemical data available in the literature on active Spanish bentonitic exploitations were done, and at the same time, new data are provided from a set of representative samples from these deposits. They were located in three different areas with different geological origins: (1) Miocene sedimentary deposits from the Tajo Basin (Madrid–Toledo provinces) in the center of the Iberian Peninsula, where bentonites appear in two different units named for their colors (Green Clays and Pink Clays); (2) samples from Tamame de Sayago (Zamora province) originating from the hydrothermal alteration of granitic Variscan rocks; and 3) Miocene deposits originating from the hydrothermal alteration of volcanic or subvolcanic rocks from the Cabo de Gata volcanic area (Almería Province) in the southern part of Spain, where the three main deposits (Cortijo de Archidona, Los Trancos, and Morrón de Mateo) were studied. The bentonites from the Tajo Basin were formed mainly by trioctahedral smectites, and there were significant mineralogical differences between the Green and Pink Clays, both in terms of the contents of impurities and in terms of smectite crystallochemistry and crystallinity. The smectites from Tamame de Sayago were dioctahedral (montmorillonite–beidellite series), and they appeared with kaolinite, quartz, and mica in all possible proportions, from almost pure bentonite to kaolin. Finally, the compositions of the bentonites from the three studied deposits in Cabo de Gata were quite similar, and zeolites and plagioclases were the main impurities. The structural formulae of the smectites from Cortijo de Archidona and Los Trancos showed a continuous compositional variation in beidellite–montmorillonite, while in Morrón de Mateo, the smectites were mainly montmorillonite, although there was continuous compositional variation from Al montmorillonites to Fe–Mg-rich saponites. The variation in the smectite composition is due to the intrusion of a volcanic dome, which brings new fluids that alter the initial composition of the smectites. View Full-Text
Keywords: bentonite; smectite; Mg clays; stevensite; saponite; montmorillonite; beidellite; kerolite bentonite; smectite; Mg clays; stevensite; saponite; montmorillonite; beidellite; kerolite
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MDPI and ACS Style

García-Romero, E.; María Manchado, E.; Suárez, M.; García-Rivas, J. Spanish Bentonites: A Review and New Data on Their Geology, Mineralogy, and Crystal Chemistry. Minerals 2019, 9, 696. https://doi.org/10.3390/min9110696

AMA Style

García-Romero E, María Manchado E, Suárez M, García-Rivas J. Spanish Bentonites: A Review and New Data on Their Geology, Mineralogy, and Crystal Chemistry. Minerals. 2019; 9(11):696. https://doi.org/10.3390/min9110696

Chicago/Turabian Style

García-Romero, Emilia, Eva María Manchado, Mercedes Suárez, and Javier García-Rivas. 2019. "Spanish Bentonites: A Review and New Data on Their Geology, Mineralogy, and Crystal Chemistry" Minerals 9, no. 11: 696. https://doi.org/10.3390/min9110696

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