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Ivory

2007 Schools Wikipedia Selection. Related subjects: Materials science

   An elaborately carved ivory decoration
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   An elaborately carved ivory decoration

   Ivory is a hard, white, opaque substance that is the bulk of the teeth
   and tusks of animals such as the elephant, hippopotamus, walrus,
   mammoth, narwhal, etc. Prior to the introduction of plastics, it was
   used for billiard balls, piano keys, bagpipes, buttons and ornamental
   items. The word "ivory" was traditionally applied to the tusks of
   elephants; in fact, the word is ultimately from Ancient Egyptian âb,
   âbu "elephant". Plastics have been viewed by piano purists as an
   inferior ivory substitute on piano keys, although other recently
   developed materials more closely resemble the feel of real ivory.

Structure

   The chemical structure of the teeth and tusks of mammals is the same
   regardless of the species of origin, and the trade in certain teeth and
   tusks other than elephant is well established and widespread.
   Therefore, "ivory" can correctly be used to describe any mammalian
   teeth or tusks of commercial interest which is large enough to be
   carved or scrimshawed.

Teeth and tusks

   Pacific Walrus at Cape Peirce
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   Pacific Walrus at Cape Peirce
   Section through the ivory tooth of a mammoth
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   Section through the ivory tooth of a mammoth

   Teeth and tusks have the same origins. Teeth are specialized structures
   adapted for food mastication. Tusks, which are extremely large teeth
   projecting beyond the lips, have evolved from teeth and give certain
   species an evolutionary advantage. The teeth of most mammals consists
   of a root and the tusk proper.

   Teeth and tusks have the same physical structures: pulp cavity,
   dentine, cementum and enamel. The innermost area is the pulp cavity.
   The pulp cavity is an empty space within the tooth that conforms to the
   shape of the pulp.

   Odontoblasts line the pulp cavity and are responsible for the
   production of dentine. Dentine, which is the main component of carved
   ivory objects, forms a layer of consistent thickness around the pulp
   cavity and comprises the bulk of the tooth and tusk. Dentine is a
   mineralized connective tissue with an organic matrix of collagenous
   proteins. The inorganic component of dentine consists of dahllite.
   Dentine contains a microscopic structure called dentinal tubules which
   are micro-canals that radiate outward through the dentine from the pulp
   cavity to the exterior cementum border. These canals have different
   configurations in different ivories and their diameter ranges between
   0.8 and 2.2 micrometres. Their length is dictated by the radius of the
   tusk. The three dimensional configuration of the dentinal tubules is
   under genetic control and is therefore a characteristic unique to the
   order.

Ivory art in the ancient world

   Paleolithic Cro-Magnon man, during the late stages of the ice age, were
   the first to carve in ivory (mammoth tusks). Both the Greek and Roman
   civilizations used large quantities of ivory to make high value works
   of art, precious religious objects, and decorative boxes for costly
   objects. Ivory was often used to form the whites of the eyes of
   statues. The Syrian and North African elephant populations were reduced
   to extinction, probably due to the demand for ivory in the Classical
   world.
   Ivory has been a most prestigious material for carving.
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   Ivory has been a most prestigious material for carving.

   Tooth and tusk ivory can be carved into an almost infinite variety of
   shapes and objects. A small example of modern carved ivory objects are
   small statuary, netsukes, jewelry, flatware handles, furniture inlays,
   and piano keys. Additionally, warthog tusks, and teeth from sperm
   whales, orcas and hippos can also be scrimshawed or superficially
   carved, thus retaining their morphologically recognizable shapes.

Availability

   Due to the rapid decline in the populations of the animals that produce
   it, the importation and sale of ivory in many countries is banned or
   severely restricted. Much of the decline in population is due to
   poachers during and before the 1980s. Since the worldwide ivory trade
   ban in 1989 there have been ups and downs in elephant populations, and
   ivory trade as bans have been placed and lifted. Many African countries
   including Zimbabwe, Namibia and Botswana claim that ivory trade is
   necessary—both to stimulate their economies and reduce elephant
   populations which are allegedly harming the environment. In 2002 the
   United Nations partially lifted the ban on ivory trade, allowing a few
   countries to export certain amounts of ivory. Yet, a 1999 study done by
   Oxford University found that less than one percent of the five-hundred
   million US dollars ivory sales generated ever reach Africans; most of
   it goes to middlemen and vendors, so the effectiveness of the policy is
   in question.

   Kenya, which saw its elephant populations plummet in the decade
   preceding the 1989 ban, claims that legalizing ivory trade anywhere in
   Africa will endanger elephants everywhere in Africa as poachers would
   attempt to launder their illegal ivory with legal stockpiles.

   The 2006 Zakouma elephant slaughter in Chad is one of a long series of
   massacres which have eliminated 97 percent of the original 300,000
   African elephant population of Chad in only four decades.

   The demand for ivory is primarily from the Japanese hanko industry.
   Hankos are small seals. Traditionally, these hankos were also made from
   other material. Ivory hankos were introduced only in the last century.

   Trade in the ivory from the tusks of dead mammoths has occurred for 300
   years and continues to be legal. Mammoth ivory is used today to make
   handcrafted knives and similar implements.

   A species of hard nut is gaining popularity as a replacement for ivory,
   although its size limits its usability. It is sometimes called
   vegetable ivory, or tagua, and is the seed endosperm of the ivory nut
   palm commonly found in coastal rainforests of Ecuador , Peru and
   Colombia.

Types of ivory

     * Elephant and mammoth ivory from the tusks of bull elephants and
       mammoths.
     * Walrus ivory from the tusks of a bull walrus.
     * Sperm Whale and Killer Whale ivory
     * Narwhal ivory
     * Hippopotamus ivory
     * Warthog ivory
     * Elk Ivory from the bugling teeth of bull elk.

   So-called hornbill ivory, derived from a bird, is not true ivory but
   resembles it in some ways.

   Retrieved from " http://en.wikipedia.org/wiki/Ivory"
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   with only minor checks and changes (see www.wikipedia.org for details
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