Natural Science in Archaeology

162 7 Metals and Related Minerals and Ores
remain somewhat in question. Lechtman believes the arsenic minerals were most
likely enargite and arsenopyrite. Arsenic compounds have been known since the
first millennium BCE. Aristotle refers to sandarach (As 2 S 3 ) in the fourth century
BCE. In the first century CE, Pliny stated that sandarach is found in gold and silver
mines. In the early first millennium CE, inhabitants of the north coast of Puerto
Rico were alloying copper, gold, and silver in a ratio of 55 Cu/40 Au/5 Ag (Siegel
and Severin 1993).
The most interesting questions involve the early arsenical coppers. Analyses
from dozens of early metallurgical centers have shown that arsenic bronzes were
fairly common in the Chalcolithic and early Bronze Age. The most intriguing question
is how the metalsmith discovered the technology of alloying arsenic with copper.
The “problem” of early copper-arsenic alloys is widespread. For example, see
the article on the North Caucasus by Ravich and Ryndina (1995). The use of arsenic
was not only widespread, it was intensive. In a fourth millennium BCE Near
Eastern (Nahal Mishmar) hoard of copper objects, 24 of the 36 analyzed had an
average arsenic content of 5.23% (Muhly 1977). An ancient copper mine from the
southern Sinai contains the copper arsenides koutekite (Cu 5 AsS 2 ) and domeykite
(Cu 3 As) associated with native copper. Ilani and Rosenfeld (1994) suggest that this
mine might be the source for the high arsenic (2–12%) Chalcolithic copper hoard
at Nahal Mishmar.
Unlike lead, there is no evidence that arsenic was ever used as a metal (and
native arsenic is very rare), and arsenic has never been found as an ingot (such as
copper and tin). Thus, arsenic must have become alloyed with copper because of the
smelting of complex ores containing both copper and arsenic.
There seems to be a consensus among archaeometallurgists that the first copper
minerals smelted were the hydroxycarbonates (malachite and azurite) and the
oxides (cuprite and tenorite), yet the first alloys were arsenical. McKerrell and
Tylecote (1972) and many others have suggested that the metallic-looking complex
copper-arsenic sulfide mineral tennantite is the most likely source of the arsenic.
However, tennantite would come from the lower unoxidized zone (along with many
metallic-looking copper sulfides).
The most likely raw materials are arsenates from the oxidized zone of ore
deposits. The following arsenates are all associated with malachite in the oxidized
zone of copper deposits in Europe, the Near East (including the former USSR),
and elsewhere: olivenite Cu 2 (AsO 4 )(OH), clinoclase Cu 3 (AsO 4 )(OH) 3 , tyrolite
CaCu 5 (AsO 4 ) 2 (CO 3 )(OH) 4 ·6H 2 O, mimetite Pb 5 (AsO 4 ) 3 Cl, adamite Zn 2 (AsO 4 ) 2 ·(OH),
erythrite Co 3 (AsO 4 ) 2 ·8H 2 O, and annabergite Ni 3 (AsO 4 ) 2 ·8H 2 O. Use of the last
four could account for the occasional high Pb, Zn, Co, or Ni contents of arsenic
bronzes. In addition to arsenic, there is the question of the related element, antimony,
finding its way into second and first millennium BCE bronzes in the Far East.
The percentages of antimony suggest that ores containing tetrahedrite (Cu 12 Sb 4 S 13 )
were used.
Bronze-making was a major industry during China’s Shang Dynasty. The last
capital of the Shang at Anyang was a particularly prolific site for bronze-making.
For raw materials there were three copper mines and four tin mines within 100 km