An acid-extraction method for analyzing the composition of ceramics produces highly precise results capable of intraregional discrimination of production loci. The method is safe, inexpensive, minimally destructive, and uses widely available instrumentation. It produces results that are highly useful in archaeological interpretation as illustrated by selected case studies.

No abstract

During the Classic period (AD 1280(AD -1450, prehistoric native Americans used turquoise for adornment, pigment and rituals at the Salado Platform Mound communities of the Tonto Basin in central Arizona. These rare, but valued, artefacts were obtained through social and trade connections to settlements and resource zones in adjoining and distant areas. We systematically examine the chemical signatures of turquoise artefacts to assess differences in access to turquoise sources between two large, competing Platform Mound communities (Cline Terrace Mound and Schoolhouse Point Mound) and determine whether they shared the same trade network. PIXE (proton-induced x-ray emission) is used to non-destructively characterize the chemical signatures of the turquoise artefacts; x-ray diffraction is used on a subset of artefacts to precisely identify mineralogical variability within copper-based blue-green minerals. Examples of multiple and mixed phases are further examined. These controlled chemical and mineralogical studies are used to guide the PIXE analysis of the larger dataset and to assess differences in source accessibility between the Cline Terrace and Schoolhouse Point Platform Mounds. Results indicate differential access to turquoise sources, similar to obsidian and decorated ceramics, and further delineate the regional social networks of this prehistoric culture.

Salado-polychrome ceramics, marked by distinctive black on white with red designs (Figure 1), coincided with the development of platform-mound communities and were the result of an amalgamation of technological traditions that occurred during a time of population movements and cultural changes in the prehistoric American Southwest. Saladopolychrome ceramics were the most abundant decorated ware of the Classic period (A.D. 1275–1450) and have been recovered from sites in central Arizona, southwestern New Mexico, and northern Chihuahua, including the site of Casas Grandes. Several archaeologists have interpreted Salado-polychrome designs as symbols of a regional cult (Adams, Crown, Rice) that eased the integration of diverse populations in times of migration and social stress. The color scheme and designs of Salado polychrome are distinctive compared to other contemporary and earlier ceramics, making definition of its development difficult.

There are some fundamental errors in the arguments of our critics: equating acid extraction with bulk techniques; confusing extractability, the signal of interpretive interest, with analytical error; and, most importantly, presuming that the influences of behavioral choices of prehistoric potters are unwanted “noise” in the data. In confirmation of our original statements, Neff et al., demonstrate that neutron activation analysis (NAA) and acid extraction are independent methods, that the data are not commensurate, and that acid extraction is sensitive to technological choices of prehistoric potters. We agree emphatically. Because ceramic vessels are not idealized geologic materials mined from quarries, but complex technological products, richly embedded with behavioral attributes, we see this behavioral sensitivity of acid extraction as its virtue, not its vice. Acid extraction is a viable compositional tool currently producing significant archaeological results.