Natural Science in Archaeology

236 10 Abrasives, Salt, Shells, and Miscellaneous Geologic Raw Materials
Cowries are small gastropods with as many as two hundred different species.
The word “cowrie” is from the Hindi and Urdu languages. Cowrie species vary in
size from less than 1 cm to more than 4 cm. Most cowries used as money were about
1.5 cm long. Used both as money and strung as beads in a necklace, cowrie shells
were quite durable. The earliest references to the use of cowrie shells come from
China where they were in circulation as early as the second millennium BCE during
the Shang Dynasty (Chang 1980). One Shang tomb in Shantung Province contained
3790 cowrie shells (Chang 1977).
Cowries were circulating in Africa by the tenth century. However, their use did
not peak until the early 1500s, when the Portuguese imported cowries to West Africa
to finance the slave trade. These cowrie shells were harvested in the lagoons of the
Maldive Islands in the Indian Ocean but found their way to West Africa (Hogendorn
and Johnson 1986). The Dutch and English began shipping cowries for the same
purpose in the 1600s. Cowries could be used as ballast in ships and subsequently
traded for a cargo of slaves (Rosenberg 1992). Cowries as money were circulated in
parts of Africa until about 1900.
A number of indigenous peoples of North America had currency or barter systems
that included the exchange of shells. For example, the Nootka of British Columbia
collected Antalis pretiosum both as food and for its shells, which were traded with
neighboring tribes to the south. The Yurok and Tolowa peoples of northern California
used strings of tusk shells as money. The value of the string was based on the length
of the string, and the number and size of the shells. The Pomo people of the central
California coast used strings of beads made from the shell of the Pismo clam (Tivela
stultorum) as currency. A higher value was placed on cylindrical beads made from
the thickest part of the shell. On the northeastern seaboard, beaded belts made from
the quahog (Mercenaria mercenaria) were used for ceremonial exchanges by native
peoples. Purple beads were more highly valued than white since only a small part
of the quahog shell is purple. These objects eventually became used as currency
under Dutch and British colonialism (Rosenberg 1992). Thus, the Dutch were able
to “purchase” the Island of Manhattan for a nominal amount of trade goods, which
may have included shell beads.
Perhaps one of the best-documented exchange networks involving shells is the
“kula” trade system of the New Guinean Trobriand Islands. A detailed ethnographic
study of the kula was published by Malinowski (1922). The kula is a highly evolved
ceremonial network principally involving the exchange of “arm-shells” made from
the Conus millepunctatus and necklaces made from beads of red spondylus shell.
According to Malinowski (1922) these goods always travel in one direction along
the trade route. The tasks involved in the manufacture of exchange articles are differentiated
by gender, and the finished articles are only exchanged by Trobriands of
high social status.
Coral. Coral is a calcareous substance secreted as a skeleton by many kinds
of marine polyps. Corals are composed of small fibers or granules of aragonite
(CaCO 3 ) or calcite (also CaCO 3 ). Calcite corals are those that form in the deep sea.
Modern reef-building corals are chiefly aragonite. Coral is found in various shades
of red, white, pink, black, and rarely yellow. The name originates from Greek