Materials, archaeological stone artifacts

This chapter is an overview of the wide variety of archaeological studies conducted by chemists. From the earliest stone artifacts to the artistic manuscripts and textiles of the more recent past, the studies presented in this volume show the wide range of materials that have been studied by chemical techniques. The field keeps expanding as chemists help provide information valuable in the interpretation of archaeological sites and artifacts. Besides helping to detect fraudulent artifacts and artistic objects in museum collections, chemists have studied the physicochemical deterioration processes that destroy the monuments and objects of the past. Thus, the role of chemists is more than just discovery of the past it includes investigation that may help preserve the artifacts for future generations to enjoy and study. 

The workhorses of analytical chemistry (atomic absorption, x-ray fluorescence, and neutron activation analyses) continue to provide mainstream contributions to our understanding of pottery, glass, metal, and stone artifacts. Stronger attention is now also directed to archaeological soils, to bone and shell, to inks and pigments, and to organic materials such as gums, lacquers, and textiles. 

In an actual apphcation, a small sample, 5-10 mg or more, would be taken from an artifact and crashed to a powder and mounted in the middle of the diffractometer. As the detector, as shown in Fig. 4.41, rotates around the sample, the computer counts the intensity of the X-rays at each angle and reports them in a graph as shown in Fig. 4.42. The angles at which the sample diffracts X-rays are then listed, along with their relative intensities, and compared to those in the searchable database. The computer then presents the closest matches to know minerals. In the example here, the material from an archaeological stone bowl is identified as the mineral chlinochlore. 

THE need for precise methods of identifying the species of origin of a blood stain or tissue fragment found in an archaeological setting is well documented. In his analysis of stone tools of various types and materials, Loy (1) detected surface blood deposits on 86% of the samples. These artifacts... 

Of great use in such investigations are artifacts or materials that come from a known location. It is in this area that archaeological chemistry has made an enormous contribution. There are many cases of such movement in exotic materials, often in the form of rare stones or minerals. There were no natural sources of turquoise in ancient Mexico, for example, but tins beautiful blue-green stone was imported from the present state of New Mexico and used in the costumes and jeweliy of the elite in Aztec Mexico.. Archaeological chemistry had documented the sources of turquoise in the southwestern and found objects from Mexico that clearly came from those quarries. This example is discussed in more detail in Chap. 8, Case Studies. 

In Europe and the Middle East, the appearance of copper artifacts in the archaeological record is significant enough that the term Chalcolithic - or Copper Age -was added to the tripartite stone-bronze-iron age system. Other regions such as the upper peninsula of Michigan, which has an abundance of native copper, also recognize ancient Copper cultures (Fig. 3.7). Copper must have been an attractive and useful material to prehistoric peoples. The earliest examples of copper are in the form of pendants and jewelry. 

Residue Traces of physical and chemical remains on archaeological materials such as pottery, stone tools, and other artifacts. 

Ceramic materials constitute some of the earliest artifacts of humankind. This is not surprising since ceramics are made of the stuff of the earth, the clay-like material that can be found almost anywhere. It is even less surprising when we consider that all ceramic materials are noted, once fired, for their durability, hardness and resistance to attack by heat and corrosive substances. And even less surprising when we realize that ceramic materials constitute the major finds in almost aU archaeological digs, even the most ancient—apart from stone-working, pottery manufacture is the oldest of aU manufacturing techniques. 

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