Chemistry Reference
In-Depth Information
BIOINORGANIC
MATERIALS
BONE, IVORY AND SHELL;
PHYTOLITHS
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Bone
is, after stone and pottery, probably the most frequently recovered
material in archaeological excavations. Its composition and structure provide
much information on the animals of which the bones were originally part,
serving as indicators of their anatomical and physiological characteristics,
dietary habits, age, pathological affections and, since the 1990s, of their
genetic traits. Much scientific endeavor is therefore devoted to deriving
anatomical, physiological, chronological, pathological, and genetically
related evidence from the composition and structure of ancient bones (Mays
1998; Larsen 1997).
Bone and shell are hard and resilient
composite materials
(see Textbox 32)
that form the skeleton of the body of animals.
Bone
makes up most of the
skeletons of all vertebrate and some invertebrate marine animals;
shell
is the
main component of the exoskeletons of many marine invertebrates (mol-
lusks, echinoderms, and crustaceans) as well as the encasement of avian
eggs. Both these materials consist of a structural framework made up of
essential organic substances interwoven with
bioinorganic materials
, also
known as
biominerals
; see Table 64. The
biominerals
are somehow intriguing
substances that challenge the perception (based on the historical, but erro-
neous, definition of inorganic and organic substances) that biological mate-
rials are made up exclusively of
organic
substances created by living
organisms, while inorganic substances belong solely to the inanimate world.
Although the composition of the biominerals is inorganic, they are biologi-
cal materials, created by living organisms. Thus the biominerals link the
apparently lifeless inorganic compounds to the living world.
Bone, shell, and coral are not, however, the only biominerals created by
living organisms. The kidney and liver of animals, for example, often syn-
thesize biominerals in the form of pathological stones (known as
calculi
)
of varied composition (mostly of calcium oxalate, calcium phosphate, or
