Elephant and mammoth tusk ivory comes from the two modified upper incisors of extant and extinct members of the same order (Proboscidea). African and Asian elephants are both extant. Mammoths 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 which consistently provides high quality, carvable ivory. For other uses, see Elephant (disambiguation). ... Species Mammuthus africanavus   African mammoth Mammuthus columbi   Columbian mammoth Mammuthus exilis   Pygmy mammoth Mammuthus jeffersonii   Jeffersonian mammoth Mammuthus trogontheri   Steppe mammoth Mammuthus meridionalis Mammuthus primigenius   Woolly mammoth Mammuthus lamarmorae   Sardinian Dwarf Mammoth A mammoth is any of a number of an extinct genus of elephant, often with long curved tusks... Pacific Walrus at Cape Peirce A tusk is an extremely long tooth of certain mammals that protrudes when the mouth is closed. ... This article or section does not cite its references or sources. ... Incisors are the first kind of tooth in heterodont mammals. ... Groups Jozaria (extinct) Anthracobunidae (extinct) Moeritheriidae (extinct) Euproboscidea Numidotheriidae (extinct) Barytheriidae (extinct) Deinotheriidae (extinct) Elephantiformes Phiomiidae (extinct) Palaeomastodontidae (extinct) Hemimastodontidae (extinct) Euelephantoidea Choerolophodontidae (extinct) Amebelodontidae (extinct) Gnathabelodontidae (extinct) Gomphotheriidae (extinct) Elephantidae Mammutidae (extinct) Proboscidea is an order containing only one family of living animals, Elephantidae, the elephants, with three species... Species Loxodonta adaurora (extinct) Loxodonta africana Loxodonta cyclotis African elephants are the two species of elephants in the Loxodonta genus, one of the two existing genera in Elephantidae. ... Binomial name Elephas maximus Linnaeus, 1758 Asian Elephant range The Asian Elephant (Elephas maximus), sometimes known by the name of its nominate subspecies (the Indian Elephant), is one of the three living species of elephant, and the only living species of the genus Elephas. ... Species Mammuthus africanavus   African mammoth Mammuthus columbi   Columbian mammoth Mammuthus exilis   Pygmy mammoth Mammuthus jeffersonii   Jeffersonian mammoth Mammuthus trogontheri   Steppe mammoth Mammuthus meridionalis Mammuthus primigenius   Woolly mammoth Mammuthus lamarmorae   Sardinian Dwarf Mammoth A mammoth is any of a number of an extinct genus of elephant, often with long curved tusks... Official language(s) English Capital Juneau Largest city Anchorage Area  Ranked 1st  - Total 663,267 sq mi (1,717,855 km²)  - Width 808 miles (1,300 km)  - Length 1,479 miles (2,380 km)  - % water 13. ... Siberian Federal District (dark red) and the broadest definition of Siberia (red) Udachnaya pipe Siberia (Russian: , Sibir; Tatar: ) is a vast region of Russia constituting almost all of Northern Asia. ... ...

An African elephant tusk can grow to 3.5 meters in length. 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. Tooth enamel is the hardest and most highly mineralized substance of the body , and with dentin, cementum, and dental pulp is one of the four major parts of the tooth. ... Dentin (BE: dentine) is the name of substance between the enamel (crown) or cementum (root) of a tooth and the pulp chamber. ... Cementum is a specialized bony substance covering the root of a tooth. ...

Polished cross-sections of elephant and mammoth ivory dentine display uniquely characteristic Schreger lines. 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 discernable 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 angles and convex angles. 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 ^[1]. Schreger lines are visual artifacts that are evident in the cross-section of ivory. ...

Notes

1. ^ http://www.lab.fws.gov/Ivory/elephant.html