Series editors' preface - Wood Tools

Figure 5.2 Sources of ivory that have been exploited
commercially: elephant (1), mammoth (2), hippopotamus
(3), walrus (4), wart hog (5), sperm whale tooth (6).
Item 7 is a sailors fid (a tapering pin used to open the
strands of a rope before splicing) made from the jaw
bone of a sperm whale
(Loxodonta africana) and the Asian or Indian
elephant (Elephas maximus). The tusks of the
African elephant grow to a larger size than
those of the Indian elephant, are carried by
both sexes and are generally of a whiter
colour. The female Indian elephant may carry
very small tusks but these do not often
protrude from behind the lips. The tusks of a
mature African bull elephant may reach a
weight of 70–90 kg and a length of 2–2.5 m.
For Indian male elephants a tusk may reach
only 1.5 m in length and weigh 25–40 kg
(Kühn, 1986). Mammoth tusks can be up to
5 m long and weigh up to 150 kg each.
Elephants are currently restricted to small
portions of their original ranges, which
included virtually all of Africa, the Middle East
and Asia. Trade in elephant ivory is ancient
and was surprisingly widespread with elephant
ivory showing up as far north as Britain and
Germany during the Roman period. During the
past few centuries the trade in ivory has
focused on the African elephant, with huge
quantities being exported during the
nineteenth and twentieth centuries (Tomlinson,
1862). In recent years the trade in ivory
has been restricted and the transfer of objects
containing ivory across international boundaries
is currently monitored and controlled.
Walruses range around the world in the
Arctic latitudes and produce large tusks of
Other materials and structures 195
even colour and texture. Walrus ivory has
been traded almost as far southward as
elephant ivory was traded northward and was
always a source for ivory workers in the northern
latitudes. Ivory from the mammoth species
Mammuthus primigenus was a northern ivory
source found in well-preserved permafrost
deposits in Siberia and used extensively in the
nineteenth century when the trade in ivory
reached large proportions. During a visit to the
London dock warehouses in 1899 Tomes
noted 130 tons of elephant ivory and about
ten tons of mammoth tusks. The price of
mammoth ivory then was only a quarter of the
price of elephant ivory (Tomes, 1923). It is
thought that the tusks of at least 45 000
mammoths have been sold in the last 300
years (Krzyskowska, 1990). It has further been
estimated that in recent years only one-quarter
of commercial ivory has been obtained from
freshly killed elephants and that the remainder
derives from extinct proboscidea (Edwards
et al., 1998).
Tusks (elephant and mammoth) are modified
elongated incisor teeth, found only in the
upper jaw, the premaxilla. In other animals
tusks may possibly be found elsewhere but
they are still teeth. They all share a common
composition and structure of inorganic salts
deposited within a protein matrix composed
predominantly of collagen. All vertebrate
mineralized tissues have a form of calcium
phosphate as the main inorganic constituent.
The inorganic component of human dentine is
mainly hydroxyapatite Ca 10(PO 4) 6OH 2. Ivory
has long been thought to be built up from
hydroxyapatite as well. However, it has been
shown that a more correct composition of the
inorganic component of proboscidean ivory is
given by dahllite. Dahllite is also a calcium
phosphate mineral but with the formula
Ca 10(PO 4) 6 (CO 3)H 2O (Matienzo and Snow,
1986). Different sources suggest varying
organic/inorganic ratios in dentine. The organic
part is normally said to be around 35–40%
(Webster, 1958). However, a recent examination
has shown the protein content of African
ivory to be on average 30% greater than that
of Indian ivory (Edwards et al., 1998).
Teeth are composed of three structurally
distinct materials – enamel, dentin and cementum
(Figure 5.3). When present, enamel forms
a thin but very hard outer covering. Dentin is