Caracterización mineralógica y química de los ladrillos de la Torre del Oro de Sevilla: una aproximación a la temperatura de cocción y origen de las materias primas

Abstract

La Torre del Oro es un edificio almohade del siglo XIII de tres cuerpos, con fábrica de ladrillo en el segundo y tercer cuerpo. De acuerdo con el análisis mineralógico se han diferenciado dos grupos de ladrillos. El primero se caracteriza por la presencia de illita y el desarrollo incipiente o nulo de fases de alta temperatura (gehlenita, wollastonita). Presentan coloraciones rojizas y pasta con textura microcristalina. Estos ladrillos se cocieron entre 800-850ºC. Para el segundo grupo la temperatura de cocción se encuentra entre 850-900ºC, según se deduce de la ausencia de illita y de la presencia en cantidades importantes de gehlenita y wollastonita-diopsido. La pasta es verde oscura e isótropa, presentando los ladrillos colores claros. El estudio de la evolución de las fases en los ladrillos calentados en el laboratorio a 800 y 900ºC concuerda razonablemente con los már-genes de cocción deducidos del estudio mineralógico. La composición química de los ladrillos es muy homogénea y similar a la de los materiales terciarios de la Formacion Écija (margas azules) y de ciertos niveles de la Serie de Transición, ambos con afloramientos muy próximos a Sevilla, que pudieron ser empleados para la fabricación de estos ladrillos. Palabras clave: Torre del Oro, ladrillos, temperatura de cocción, margas azules Mineralogical and chemical characterization of the bricks from the Torre del Oro, Seville (Spain). An approach to firing temperature and the origin of the raw materialsThe Torre del Oro is a Moslem building of three bodies dating from the 13th Century. The second and third bodies are built with bricks. According to mineralogical analysis two main groups of bricks can be established. A first group of bricks contents illite and low amounts of gehlenite and wollastonite. They are reddish and present a mycrocristalline matrix. The firing temperature ranges between 800-850ºC for this group. Firing temperatures for the second group ranged between 850-900ºC, because of the absence of illite, and the presence of important amounts of gehlenite and wollastonite-diopside. They are yellowish and present a green coloured isotropic matrix. Mineralogical compositions of laboratory firing samples at 800ºC and 900ºC agree reasonably with the estimated firing temperature. Chemical composition presents no differences among the samples, being quite similar to Tertiary sediments from the Ecija Formation (blue marls) and the Transition Series (silts). These materials crop out quite near Seville, and have been traditionally used in the local tile industry.

Application of XRF, XRD, thermal analysis, and voltammetric techniques to the study of ancient ceramics

“…This high loss on ignition, probably because the biscuits analyzed contained undecomposed CaCO 3 , did not occur for similar materials from the Guadalquivir River basin studied by Sanchez et al [16] and Gonzalez [17] or for tiles from Torre del Oro (Seville, Spain) studied by Leguey et al [18].…”

Multidisciplinary study of glazed ceramics from Chamberí Metro Station (Madrid, Spain): A knowledge base with technological and heritage value

“…These clays, generically referred to as Moro clay, are rich in quartz -due to their proximity to the paleozoic metamorphic basement-and have a low carbonate content (Alonso-Azcárate et al, 1997;Jordán et al, 1999Jordán et al, , 2009. The clays traditionally used in the ceramics industry in Seville, in which Triana was the main production centre, were Tertiary illitic calcareous clays from the banks of the River Guadalquivir, with sandy materials from the quaternary alluvium (González-García and García Ramos, 1966, González-García et al, 1988, 1990Flores et al, 1999;Leguey et al, 2001;Rincón et al, 2008). There is documentary evidence of single firing of lead glazes in later stages of Al-Andalus, while double firing was predominant in the Caliphate and Taifa periods (Coll Conesa, 2014).…”

“…2). The compositions of clayey materials and fired products from different outcrops in the province of Castellón are plotted in black: 1) Miocene clays from Sitjar (Sanfeliu et al, 1989), 2) Fired products from cre-taceous clays (Jordán et al, 1999), 3) Permo-Triassic Moro clays -lower (a), middle (b) and upper (c) Units (Jordán et al, 2009), and from the province of Seville in red: 1) Illitic-calcareous clays (González-García et al, 1988), 2) Mixtures of calcareous and non-calcareous clays (González-García et al, 1990), 3) Industrial bricks -red (a) and yellow (b)- (Flores et al, 1999), 4) Bricks from the Torre del Oro in Seville (Leguey et al, 2001) and 5) Brick from the Reales Alcázares, in Seville (Rincón et al, 2008). If the CT O and QR O pieces were made with clays from different outcrops in the province of Castellón (in black), they must also have been mixed with clayey materials that were especially calcareous and poor in silica.…”

Estudio arqueométrico de cerámicas procedentes de cinco alfares celtibéricos del sistema ibérico central

“…La asociación mineralógica detectada corrobora y amplía las observaciones realizadas bajo el microscopio óptico. Así, es preciso advertir que la mayor parte de la calcita detectada por DRX se refiere a la fase secundaria precipitada durante el enterramiento y que la original, observada bajo el microscopio en forma de grumos o nodulizaciones de reacción, ha sufrido también recarbonatación (17).…”