Elephant and mammoth ivory: Difference between revisions
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#REDIRECT [[Ivory]] |
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[[Image:ADIM 6301 big.JPG|thumb|250px|Mammoth Ivory tusk carved by Japanese master carver]] |
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'''Elephant and mammoth tusk ivory''' comes from the two modified upper [[incisors]] of extant and extinct members of the [[Order_(biology)|order]] [[Proboscidea]]. [[Mammoth]]s are believed to have been extinct for 10,000 years. Because of the geographical range in [[Alaska]] and [[Siberia]], ''[[Mammuthus primigenius]]'' tusks have been well preserved. Therefore, ''Mammuthus primigenius'' is the only extinct [[proboscidan|Proboscidea]] which consistently provides high quality, carvable [[ivory]]. |
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An African elephant tusk can grow to 3.5 metres in length. [[Tooth enamel|Enamel]] is only present in the tusk tip in young animals. It is soon worn off and not replaced. Whole cross-sections of proboscidean tusks are rounded or oval. [[Dentine]] composes 95% of the tusk and will sometimes display broad concentric bands. [[Cementum]], which can be thick in extinct genera, covers the outside of the tusk. Cementum can present a layered appearance, particularly in mammoth. |
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Polished cross-sections of elephant and mammoth ivory dentine display uniquely characteristic [[Schreger line]]s. Schreger lines are commonly referred to as cross-hatchings, engine turnings, or stacked chevrons. Schreger lines can be divided into two categories. The easily seen lines which are closest to the cementum are the outer Schreger lines. The faintly discernible lines found around the tusk nerve or pulp cavities are the inner Schreger lines. The intersections of Schreger lines form angles. These Schreger angles appear in two forms: [[concave angle]]s and [[convex angle]]s. Concave angles have slightly concave sides and open to the medial (inner) area of the tusk. Convex angles have somewhat convex sides and open to the lateral (outer) area of the tusk. Outer Schreger angles, both concave and convex, are acute in extinct proboscidea and obtuse in extant proboscidea.<ref>http://www.lab.fws.gov/ivory_natural.php#elephant</ref> |
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[[Image:ADIM 6298 big.JPG|center|thumb|550px|Mammoth Ivory tusk carved by Japanese master carver]] |
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==See also== |
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*[[Ivory trade]] |
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==References== |
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{{reflist}} |
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==External links== |
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*[http://www.antiquespider.com/information/legalauctions.asp The Auctioning of Elephant Ivory] |
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[[Category:Ivory]] |
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Latest revision as of 08:26, 5 June 2017
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