Clay sources

Table 6. Rare-Earth Oxide Distribution in Mineral and Clay Sources, wt ...

For the reasons outlined above, outcrops of workable obsidian are relatively few in number and are restricted to areas of geologically recent lava flows. Most sources are therefore reasonably well known, and, because of these constraints, identification of new sources in the eastern Mediterranean region becomes ever more unlikely. This makes the exercise of characterizing archaeological obsidians an attractive proposition, since, unlike potential clay sources for pottery provenance, the existence of completely unknown sources can be (cautiously) ignored. This is, of course, subject to the requirement noted above for more detailed geochemical characterization of existing sources. 

Methodologically, inevitably some questions must always be considered. Do the control sherds adequately represent the output of all of the relevant vessels from all of the relevant kiln sites There is always potentially the problem of kiln X - an unknown (or at least, uncharacterized) kiln which is producing wares similar to those under consideration, but not included either because it has not been identified archaeologically, or because it was not known to produce the type of ware under question. This problem should be at least considered since a geochemical knowledge of the type of clay deposits being exploited may restrict the geographical extent of the possible clay sources. The question of the representativeness of the samples is more difficult. Most kiln... 

ICP MS - glass and ceramics. Glasses are extremely suitable for REE analysis, since they are made from a mixture of sand and alkali, and it is likely that the REE are characteristic of the sand source used. Similarly, ceramics are also suitable, in that the REE are likely to be characteristic of the clay source. One such study (Ford et al. 2005) has studied South Asian finewares, and has used REE profiles to compare similar vessels made at a range of different sites in Sri Lanka and southern India. 

Emerson, T. E. and Hughes, R. E. (2000). Figurines, flint clay sourcing, the Ozark Highlands, and Cahokian acquisition. American Antiquity 65 79-101. 

Material from the Gezer excavations had already been obtained. The geologist provided a sample of limestone clay local to Gezer, which however was from a deposit that had not been exposed in antiquity. Previous studies (8) have shown that the pottery at Gezer was made from the two main types of clay sources. 

Comparison of Modern Pottery with Its Known Clay Source. The... 

Groups of Gezer Sherds of Unknown Clay Sources... 

Figure 7. Archaeological sites and clay sources relevant to this research...

From the correlation between the ancient pottery and modern clay one can draw several significant conclusions in addition to the most immediately obvious one that the matching ancient pots were locally made. The amount of temper in the ancient pottery, as evidenced by our comparison with the clay source, has not diluted or otherwise significantly altered the compositional pattern of the ceramic. Also the pottery must not have significantly changed in composition during burial. In addition we observed a small but significant difference between the composition... 

THE USE OF FIRE TO transform CLAY PASTE into solid ceramic vessels may have been one of the earliest efforts at chemistry. Since the earliest times, pottery has been made by using clays formed by the weathering of rocks. Sedimentary deposits containing clay minerals also contain fragments of other minerals that are broken from the source rocks as they weather. The chemical composition of the sediments used as a clay source determined some of the characteristics of the pottery that was produced. 

In general, one can expect only the most coarse-grained patterns in a compositional data set to be readily apparent and interpretable. In the original analysis, temper-related compositional patterning was largely obscured by major chemical differences between the clay sources and the fact that temper interacted differently with the two clays represented in the data,... 

Because geochemically different clay sources may have been used by potters to produce ceramics for both domestic and trade purposes, neutron activation analysis (NAA) has been used as an independent means of ceramic characterization. Because of the relatively good analytical precision possible with NAA, statistical patterning of NAA data for major, minor, and trace element concentrations may be used as a powerful provenancing tool. 

Temporal Differences. The Solduz Valley pottery studied here covers the period from ca. 5500 B.C, to ca. 3550 B.C. The appreciable scatter in the NAA data presented in Table I raises the question of whether some of the scatter is the result of a temporal change in the chemistry of the clay sources used by potters at any or all of the three Solduz Valley sites. 

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