Authentic African elephant carved statue. 26 cm high. Pre 1978 ban. Postage R50.00

Authentic African elephant carved statue. 26 cm high with 7.5 cm base. Pre 1978 ban. BG. Shreger lines clearly visible.

Ivory identification: The ivories

ELEPHANT AND MAMMOTH (Laxodonta africana, Elephas maximus, Mammuthus)

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 eographical range in Alaska and Siberia, Mammuthus primigenus tusks have been well preserved. Therefore, Mammuthus primigenus is the only extinct proboscidean which consistently provides high quality, carvable ivory. An African elephant tusk can grow to 3.5 meters in length. Enamel is only present on the tusk tip in young animals. It is soon worn off and not replaced. Whole cross-section 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.

Polished cross-section of elephant and mammoth ivory dentine display uniquely characteristic Schreger lines.1 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 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 (Fig. 9).1

Figure 9. Photocopies of extinct (left) and extant (right) proboscidean ivory cross-sections. The outer Schreger angles (OA) are those which are in the dentine (D) closest to the cementum (C).

A photocopy machine is used to capture Schreger angles from mammoth and elephant ivory crosssections. The cross-section is placed on the glass plate of a photocopy machine.

1 Schreger lines in proboscidean dentine were described by the German anatomist Bernhard Gottlob Schreger in 1800 (Obermayer 1881) and should not be confused with Hunter-Schreger bands in enamel.