Majolica sherds

In addition to the archaeological material, majolica sherds were obtained from two modern factories in Puebla La Trinidad and Santa Maria. Both of these potteries use a clay body blended from a mixture of equal amounts of a black volcanic clay and a white marl obtained from the immediate area around Puebla (4), Samples from these sherds were analyzed by neutron activation analysis and the data used to represent a Puebla composition. 

We are most pleased to be able to use the modern majolica sherds collected by Marino Maggetti in Puebla, Mexico when he traveled there in 1981. These sherds have been of enormous value to us as a reference for the composition of majolica manufactured in Puebla. 

On the basis of the compositions obtained by neutron activation analysis two distinctive groups of pottery have been identified from the majolica sherds excavated from Spanish sites in the New World. The principal sites yielding majolica sherds analyzed in this project include Isabela, La Vega Vieja, Juandolio, and Convento de San Francisco in the Dominican Republic Nueva Cadiz in Venezuela and excavations in Mexico City at the Metropolitan Cathedral and for the Mexico City Metro transportation system. Concentrations of NazO, KzO, BaO, MnO, FezOs, RbzO, CszO, LazOs,... 

Figure 8. Computer projection of three-dimensional plot of cerium, lanthanum, and thorium oxide concentrations for Spanish Colonial majolica sherds. The data divides into a group having its source in Spain and a group whose source is Mexican, as discussed in the text.

It is logical to consider whether the majolica sherds which were found in Mexico City could have been fabricated of local clay. Fortunately data on clays and related pottery from the Valley of Mexico has been collected at Brookhaven National Laboratory over many years. The ceramic material, which had previously been anlyzed by Harbottle and Sayre in collaboration with other investigators, consisted of Precolumbian artifacts. The pottery and the clays from two archaeological sites within the Valley, Teotihuacan, and Tlatilco were all basically similar in composition, although the clays and pottery from the two separate sites could be diflFerentiated through a subtle multivariate statistical analysis. It is likely that the entire Valley of Mexico is underlain with clay bed of moderately uniform trace impurity composition, and hence if the composition of the Mexico City majolica sherds was similar to that of ceramics and clay from Teotihuacan or Tlatilco, it would be probable that the majolica was fabricated from clays originating somewhere within the Valley of Mexico. 

The high calcium content in the majolica found in Mexico City— 21.4% calculated as pure calcium carbonate compared with 5.9% in sherds of Teotihuacan—suggests that a calcium compound such as calcium or calcium magnesium carbonate may have been added to the majolica either as a temper or through deposition during burial. Petrographic examination of cross sections of representative Mexico City majolica sherds show heavy deposits of birefringent material with structures... 

Petrographic comparison of the Mexico City majolica with Teotihuacan sherds shows that except for the secondary deposition of carbonates, which is present in the majolica but absent in the Precolumbian sherds, the mineral composition of both sets of specimens is very similar. Both notably include hornblende and similar feldspars as inclusions, and both are low in quartz. Similarly, except for the calcite in the majolica, both sets of sherds show similar x-ray diflFraction patterns. The mineralogical evidence, therefore, strongly suggests that both sets of sherds were made from closely related clays and that the compositional diflEerences that exist between them are primarly the result of the accumulation of a secondary calcareous deposit within the majolica sherds during burial in the wet soil of Mexico City. 

We have been able to distinguish two distinctive groups of pottery among the majolica sherds excavated from Spanish sites in the New World. These distinctions are based on the examination and analysis of the paste portions of the sherds and have involved the combined use of neutron activation analysis, x-ray diflFraction analysis, and petrographic examination. Preliminary investigations of the relationships of each of these two groups of sherds to sherds of known origin have also been undertaken. There is evidence to support a Spanish source for the sherds from sites in the Dominican Republic and Venezuela and a Mexican source for the sherds excavated in Mexico City. 

We have been able to compare our samples to a small group of majolica sherds from Spain and to a reasonably large group of Precolumbian sherds from Teotihuacan. The majolica sherds from Caribbean sites agree in composition with the Spanish specimens, and those from sites in Mexico City have compositions sufBciently similar to the sherds from Teotihuacan, considering the secondary deposits of carbonates of calcium which are in the majolica sherds and not in the Precolumbian sherds. The presence of these deposits of carbonates of calcium in the majolica and their absence in the Precolumbian sherds was determined by petrographic examination and x-ray diflFraction as well as by elemental analysis. 

We report a new nondestructive technique using EDTA extraction and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to measure lead isotope ratios among majolica sherds from six 18 century presidios in northern New Spain. Our preliminary results support previous archaeological and chemical studies that suggest one or two production centers as the source of majolica found in New Spain. This research has broad relevance for research on lead-glazed wares, and raises specific questions regarding the production and distribution of majolica in 18 century New Spain. 

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