Chemistry Reference
In-Depth Information
artificially. When some stable isotopes are irradiated with neutrons or with
other energetic particles, they are converted into unstable, radioactive iso-
topes, some of which do not occur naturally on earth. The newly formed
isotopes can then be identified and characterized using radioactivity detec-
tion methods. This has given rise to a significant branch of analytical chem-
istry known as
neutron activation analysis
, which is often used for the study
of such materials as obsidian, glass, and pottery (see Textbox 10) (Neff
2000).
Many stable and unstable isotopes are used for studying processes
relevant in archaeology (Katzenberg 2000). Carbon-14, also known as
radiocarbon
, an unstable isotope of carbon, for example, is of prime impor-
tance for dating archaeological finds (see Textbox 55). Carbon-13, a stable
isotope of carbon, provides a tool for studying ancient diets (see Textbox
57). The heavy isotopes of oxygen, oxygen-17, and particularly oxygen-18
are of use for estimating past temperatures (see Textbox 47) (Wagner 2000).
Isotopes frequently used in archaeological studies are listed in Table 12.
1.6.
PROVENANCE OF ARCHAEOLOGICAL MATERIALS
The term
provenance
, or
provenience
, as the word is often also spelled, is used
to refer to the geographic location, that is, the area or place from which a
material or artifact originates. The main interest in the study of the prove-
nance of archaeological materials and objects is twofold: determining the
geographic source of archaeological materials, and studying the eventual
distribution of such material to other areas and the routes through which
they were traded (Hughes 1991). The study of provenance is based on the
assumption that most materials have some detectable compositional char-
acteristics that are uniquely related to their place of origin and particularly
to the nature and the relative amount of the minor and trace elements at the
place, which generally vary from place to place. To ascertain whether the
composition of a material may provide relevant information on its prove-
nance, it is necessary to ascertain three basic conditions:
1.
Different samples of the material from a single source are of uniform
composition.
2.
There are compositional differences between samples of the same
material from different sources.
3.
Such differences can be unequivocally recognized and distinguished.
