Chemistry Reference
In-Depth Information
TABLE 45
Corrosion Products Identified in Archaeological Lead
Corrosion product
Color
Oxides
Massicot (lead monoxide)
Yellow
Platnerite (lead dioxide)
Brown to black
Carbonates
Cerusite (lead carbonate)
Gray
Hydrocerusite (basic lead carbonate)
White
Chlorides
Cotunnite (lead dichloride)
White
Phosgenite (mixture of lead chloride and lead carbonate)
White
Sulfates
Anglesite (lead sulfate)
White
Sulfides
Galena (lead sulfide)
Gray
for resolving practical archaeological problems. Analyzing ancient metallic
objects and learning about their composition provides clues as to their nature
and on metallurgical operations the metals used to make them underwent
when recovered from the ores as well as during forming. Identifying the
minor components of a metal or alloy is often useful for elucidating com-
positional variations made to a metal before using it for making different
objects. The analysis of ancient ores and slags, on the other hand, provides
information on the exploitation of specific ores for the production of certain
metals and on ancient smelting techniques. Similarities and differences in
the composition of a metal smelted at different locations may even provide
guidelines to establish the provenance of the objects (Pernicka 2004).
Also the importance of the identification and analysis of
slags
, the waste
materials of metallurgical processes, often the only evidence of previous
metallurgical activity, cannot be overemphasized. Establishing the composi-
tion of slags makes it possible to determine the nature of the ores, fluxes,
and reducing agents used in particular smelting processes and to establish
whether metallurgical operations were carried out in a random fashion or
under carefully controlled conditions. Of all ancient metals, the most inten-
sively investigated so far have been copper and iron and their alloys. Much
fewer studies have been done as yet, however, on other metal and alloys,
although some research has been dedicated to the provenance of gold and
silver, much of it related to the composition of coins (Buchwald and Wivel
1998; Bachmann 1982).
