Materials, archaeological

The range of raw materials that humans use for food, construction, valuables, transportation, and other purposes is enormous. Many materials are found at archaeological sites. The Black Earth site in southern Illinois, a settlement of hunters dating from 4000 to 3000 bc provides an example. It is an enormous site, more than a city block in size, and the cultural layer is up to 1.5 m (5 ft) deep. The concentration of ash, excrement, and other organic matter in the sediments changed the chemistry of the soil, resulting in more alkaline conditions, favorable for the preservation of bone and other materials. 

Preserved plant and animal remains document the diet of the inhabitants. The Indian occupants of the site used the river, lakes, and swamps in the area for aquatic resources and exploited the uplands for deer and nuts. Hickory nutshells are very common in the middens acorn shells also occur throughout the occupation area, along with the remains of hazelnuts and walnuts. These nuts are available in 

Chert projectile point Crinoid-stem bead 

In addition to the residential area, there was a cemetery at the Black Earth site. At least 154 burials were found, sometimes buried with artifacts and other materials. A number of exotic items were found in addition to the local raw materials. One perforated disk of marine shell, probably from the Atlantic Ocean or the Gulf of Mexico, was found around the neck of a buried infant. A copper wedge from the Great Lakes area had been placed at the top of the neck of the skeleton, perhaps as a substitute for the missing skull of this particular individual. These materials had come from hundreds of miles distant to be buried at the Black Earth site. 

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Deteriora.tlon. Apart from physical damage that can result from carelessness, abuse, and vandaUsm, the main problem with metal objects Hes in thek vulnerabihty to corrosion (see Corrosion and corrosion control) (127,128). The degree of corrosion depends on the nature and age of the object. Corrosion can range from a light tarnish, which may be aesthetically disfiguring on a poHshed silver or brass artifact, to total mineralization, a condition not uncommon for archaeological material. 

E. V. Sayre and co-workers, eds.. Materials Issues in Art and Archaeology, Materials Research Society Symposium Proceedings Vol. 123, Materials Research Society, Pittsburgh, Pa., 1989. 

Bones and teeth, however, are primary archaeological materials and are common to many archaeological sites. Bones bearing cut marks from stone tools are a clear proxy for human occupation of a site, and in the study of human evolution, hominid remains provide the primary archive material. Hence, many attempts have been made to directly date bones and teeth using the U-series method. Unlike calcite, however, bones and teeth are open systems. Living bone, for example, contains a few parts per billion (ppb) of Uranium, but archaeological bone may contain 1-100 parts per million (ppm) of Uranium, taken up from the burial environment. Implicit in the calculation of a date from °Th/U or Pa/ U is a model for this Uranium uptake, and the reliability of a U-series date is dependent on the validity of this uptake model. 

It seems appropriate, therefore, to begin a survey of archaeological materials with a discussion of inorganic materials - from minerals and rocks, the most abundant materials on the planet, to those extracted, derived, or made from them, such as metals and alloys, glass and ceramics (Chapters 1-7). Organic and biological materials produced by, or derived from plants or animals are discussed next (Chapters 8-15). Finally, the atmosphere and the hydrosphere, which make up most of the environment that affects all materials and determines the way they decay, are surveyed (Chapter 17). 

Sampling archaeological materials for analytical purposes may sometimes be the most difficult stage in an analytical procedure (Bellhouse 1980 Cochran 1977). Since rock, ceramics, and cement are heterogeneous materials, obtaining a representative sample of them may be the most difficult step in a whole analytical procedure. 

Most of the essential information on archaeological materials is derived, at the present time, using physical methods of analysis. This may include the qualitative or quantitative assessment of their composition, their provenance, the techniques used for their production, and their age. Some of the most widely used methods of chemical analysis based on physical principles are succinctly reviewed in the following paragraphs. 

Neutron activation analysis (NAA) is a technique for the qualitative and/or quantitative determination of atoms possessing certain types of nuclei. Bombarding a sample with neutrons transforms some stable isotopes into radioactive isotopes measuring the energy and/or intensity of the gamma rays emitted from the radioactive isotopes created as a result of the irradiation reveals information on the nature of the elements in the sample. NAA Is widely used to characterize such archaeological materials as pottery, obsidian, chert, basalt, and limestone (Keisch 2003). 

Some radioisotopes are continuously being produced by the bombardment of atoms on the surface of the earth or in its atmosphere with extraterrestrial particles or radiation. One of these is carbon-14, also known as radiocarbon, which is widely used for dating archaeological materials (see Textbox 55). Many radioisotopes that are not primordial or are not created by natural processes are now produced artificially using specialized equipment many of the "artificial" isotopes are of use for probing and analyzing materials. 

TABLE 101a Thermal Properties of Some Archaeological Materials... 

Goffer, Z. (1996), Dictionary of Archaeological Materials and Archaeometry, Elsevier, Amsterdam. 

Heyworth, M. P., J. R. Hunter, S. E. Warren, and J. N. Walsh (1988), The analysis of archaeological materials using inductively coupled plasma spectrometry, in Slater, E. A. and J. O. Tate (eds.), Science in Archaeology, Glasgow. 

Hill, A. D., A. H. Lehman, H. Arm, and M. L. Parr (2007), Using scanning electron microscopy with energy dispersive x-ray spectroscopy to analyze archaeological materials, J. Chem. Educ. 84(5), 810-813. 

Jose-Yacaman, M. and J. A. Ascencio (2000), Electron microscopy and its application to the study of archaeological materials and art preservation, in Ciliberto, E. and G. Spoto (eds.), Modern Analytical Methods in Art and Archaeology, Chemical Analysis Series, Vol. 155, Wiley, New York, pp. 405-443. 

Nishimura, S. (1971), Fission track dating of archaeological materials from Japan,... 

Weisseman, S. U. and W. S. Williams (eds.) (1994), Ancient Technologies and Archaeological Materials, Gordon Breach, Langhorne. 

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