Natural Science in Archaeology
Natural Science in Archaeology
Natural Science in Archaeology
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
162 7 Metals and Related M<strong>in</strong>erals and Ores<br />
rema<strong>in</strong> somewhat <strong>in</strong> question. Lechtman believes the arsenic m<strong>in</strong>erals were most<br />
likely enargite and arsenopyrite. Arsenic compounds have been known s<strong>in</strong>ce the<br />
first millennium BCE. Aristotle refers to sandarach (As 2 S 3 ) <strong>in</strong> the fourth century<br />
BCE. In the first century CE, Pl<strong>in</strong>y stated that sandarach is found <strong>in</strong> gold and silver<br />
m<strong>in</strong>es. In the early first millennium CE, <strong>in</strong>habitants of the north coast of Puerto<br />
Rico were alloy<strong>in</strong>g copper, gold, and silver <strong>in</strong> a ratio of 55 Cu/40 Au/5 Ag (Siegel<br />
and Sever<strong>in</strong> 1993).<br />
The most <strong>in</strong>terest<strong>in</strong>g questions <strong>in</strong>volve the early arsenical coppers. Analyses<br />
from dozens of early metallurgical centers have shown that arsenic bronzes were<br />
fairly common <strong>in</strong> the Chalcolithic and early Bronze Age. The most <strong>in</strong>trigu<strong>in</strong>g question<br />
is how the metalsmith discovered the technology of alloy<strong>in</strong>g arsenic with copper.<br />
The “problem” of early copper-arsenic alloys is widespread. For example, see<br />
the article on the North Caucasus by Ravich and Rynd<strong>in</strong>a (1995). The use of arsenic<br />
was not only widespread, it was <strong>in</strong>tensive. In a fourth millennium BCE Near<br />
Eastern (Nahal Mishmar) hoard of copper objects, 24 of the 36 analyzed had an<br />
average arsenic content of 5.23% (Muhly 1977). An ancient copper m<strong>in</strong>e from the<br />
southern S<strong>in</strong>ai conta<strong>in</strong>s the copper arsenides koutekite (Cu 5 AsS 2 ) and domeykite<br />
(Cu 3 As) associated with native copper. Ilani and Rosenfeld (1994) suggest that this<br />
m<strong>in</strong>e might be the source for the high arsenic (2–12%) Chalcolithic copper hoard<br />
at Nahal Mishmar.<br />
Unlike lead, there is no evidence that arsenic was ever used as a metal (and<br />
native arsenic is very rare), and arsenic has never been found as an <strong>in</strong>got (such as<br />
copper and t<strong>in</strong>). Thus, arsenic must have become alloyed with copper because of the<br />
smelt<strong>in</strong>g of complex ores conta<strong>in</strong><strong>in</strong>g both copper and arsenic.<br />
There seems to be a consensus among archaeometallurgists that the first copper<br />
m<strong>in</strong>erals smelted were the hydroxycarbonates (malachite and azurite) and the<br />
oxides (cuprite and tenorite), yet the first alloys were arsenical. McKerrell and<br />
Tylecote (1972) and many others have suggested that the metallic-look<strong>in</strong>g complex<br />
copper-arsenic sulfide m<strong>in</strong>eral tennantite is the most likely source of the arsenic.<br />
However, tennantite would come from the lower unoxidized zone (along with many<br />
metallic-look<strong>in</strong>g copper sulfides).<br />
The most likely raw materials are arsenates from the oxidized zone of ore<br />
deposits. The follow<strong>in</strong>g arsenates are all associated with malachite <strong>in</strong> the oxidized<br />
zone of copper deposits <strong>in</strong> Europe, the Near East (<strong>in</strong>clud<strong>in</strong>g the former USSR),<br />
and elsewhere: olivenite Cu 2 (AsO 4 )(OH), cl<strong>in</strong>oclase Cu 3 (AsO 4 )(OH) 3 , tyrolite<br />
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),<br />
erythrite Co 3 (AsO 4 ) 2 ·8H 2 O, and annabergite Ni 3 (AsO 4 ) 2 ·8H 2 O. Use of the last<br />
four could account for the occasional high Pb, Zn, Co, or Ni contents of arsenic<br />
bronzes. In addition to arsenic, there is the question of the related element, antimony,<br />
f<strong>in</strong>d<strong>in</strong>g its way <strong>in</strong>to second and first millennium BCE bronzes <strong>in</strong> the Far East.<br />
The percentages of antimony suggest that ores conta<strong>in</strong><strong>in</strong>g tetrahedrite (Cu 12 Sb 4 S 13 )<br />
were used.<br />
Bronze-mak<strong>in</strong>g was a major <strong>in</strong>dustry dur<strong>in</strong>g Ch<strong>in</strong>a’s Shang Dynasty. The last<br />
capital of the Shang at Anyang was a particularly prolific site for bronze-mak<strong>in</strong>g.<br />
For raw materials there were three copper m<strong>in</strong>es and four t<strong>in</strong> m<strong>in</strong>es with<strong>in</strong> 100 km