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Mountain Zebra Skin. Credit: USFWS

Publications & ID Notes

INTRODUCTION | WHAT IS IVORY? | THE IVORIES | IDENTIFYING IVORY | GLOSSARY


NATURAL IVORY


ELEPHANT AND MAMMOTH

(Loxodonta africana, Elephas maximus,  Mammuthus spp.)

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 primigenus tusks have been well preserved. Therefore, Mammuthus primigenus is the only extinct proboscidan 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-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.

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.

A photocopy machine is used to  capture Schreger angles from mammoth and elephant ivory cross-sections.  The cross-section is placed on the glass plate of a photocopy machine. A  blue photocopy transparency sheet may be placed between the object and  and the glass plate to enhance the detail of the photocopy. Enlargement  of the photocopy may also improve the image and facilitate the  measurement process.

After a photocopy of the ivory  cross-section has been obtained, Schreger angles may be marked and  measured. Use a pen or pencil and a ruler to mark and extend selected  outer Schreger angle lines.

NOTE: Only outer Schreger angles  should be used in this test.
Once the angles have been marked  and extended, a protractor is used to obtain an angle measurement.  Several angles, including both concave and convex angles, should be  marked and measured. Once the angles have been marked and measured,  calculate the angle average.

Because specimens from both extinct and extant sources may present angles between 90 degrees and 115 degrees in the outer Schreger pattern area, the differentiation of mammoth from elephant ivory should never be based upon single angle measurements when the angles fall in this range.

When averages are used to represent the angles in the individual samples, a clear separation between extinct and extant proboscideans is observed. All the elephant samples had averages above 100 degrees, and all the extinct proboscideans had angle averages below 100 degrees.


elephant ivory Click to see Schreger lines in elephant ivory

mammoth ivory Click to see Schreger lines in mammoth ivory

Another feature may be used to identify mammoth ivory.  Mammoth ivory will occasionally display intrusive brownish or blue-green  colored blemishes caused by an iron phosphate called vivianite. Elephant  ivory will not display intrusive vivianite discoloration in its natural  state. It is of interest to note that when the discoloration is barely  perceptible to the eye, the use of a hand-held ultraviolet light source  causes the blemished area to stand out with a dramatic purple  velvet-like appearance. Even if discolored, elephant ivory will not  have the characteristic fluorescence of vivianite.


WALRUS

(Odobenus rosmarus)

Walrus tusk ivory comes from two modified upper canines. The tusks of a Pacific walrus may attain a length of one meter. Walrus teeth are also commercially carved and traded. The average walrus tooth has a rounded, irregular peg shape and is approximately 5cm in length.

The tip of a walrus tusk has an enamel coating which is worn away during the animal's youth. Fine longitudinal cracks, which appear as radial cracks in cross-section, originate in the cementum and penetrate the dentine. These cracks can be seen throughout the length of the tusk. Whole cross-sections of walrus tusks are generally oval with widely spaced indentations. The dentine is composed of two types: primary dentine and secondary dentine (often called osteodentine). Primary dentine has a classical ivory appearance. Secondary dentine looks marble or oatmeal-like. This type of secondary dentine is diagnostic for walrus tusk ivory.

Walrus ivory Click to see image of walrus tooth

The dentine in walrus teeth is mainly primary dentine. The center of the tooth may contain a small core of apparent secondary dentine. The dentine is completely surrounded by a cementum layer. Enamel may or may not be present according to the extent to which the tooth has been carved or worn. A cross-section of a walrus tooth will show very thick cementum with prominent cementum rings. Concentric rings in walrus teeth are due to hypercementosis. The dentine is separated from the cementum by a clearly defined narrow transition ring.

Walrus ivory Click to see image of walrus tusk


SPERM WHALE AND KILLER WHALE

(Physeter catodon and Orcinus orca)

Sperm whale teeth can be quite large. The average height is approximately twenty centimeters. Killer whale teeth are smaller. Both species display conically shaped teeth with a small amount of enamel at the tips. The rest of the tooth is covered by cementum. Whole cross-sections of killer whale and sperm whale teeth are rounded or oval (figure).

In addition, killer whale teeth show two slight peripheral indentations. The dentine is deposited in a progressive laminar fashion. As a result of this laminar deposition, killer and sperm whale teeth will show prominent concentric dentine rings in cross-section. Killer whale teeth may also display a faint rosette pattern in the dentine cross-section. The dentine is separated from the cementum by a clearly defined transition ring.

Sperm whale ivory Click to see cross section of sperm whale tooth


NARWHAL

(Monodon monoceros)

The narwhale is a rarely seen arctic whale. The male of this species has a single left tusk that is a modified upper incisor. The tusk is spirally twisted, usually in an counter-clockwise direction. In a mature specimen the tusk can be from two to seven meters long.

Enamel may be present at the tip of the tusk. The cementum frequently displays longitudinal cracks which follow the depressed areas of the spiral pattern. As a result, narwhal tusk cross-sections are rounded with peripheral indentations. The cementum is separated from the dentine by a clearly defined transition ring. Like killer and sperm whale teeth, the dentine can display prominent concentric rings. The pulp cavity extends throughout most of the length of the tusk giving cross-sections a hollow interior.

Narwhal tusk Click to see cross section of narwhal tusk


HIPPOPOTAMUS

(Hippopotamus amphibius)

Upper and lower canine and incisors are the most common sources for hippo ivory. Each type of tooth has distinctive gross morphology. Close examination of a cross-section of hippo dentine with the aid of a 10X hand lens reveals a tightly packed series of fine concentric lines. These lines can be regularly or irregularly spaced. The orientation of the lines will follow the overall shape of the particular tooth. The center of the tooth may display an interstitial zone (TIZ). This interstitial zone represents the growth convergence of the developing dentine.

The hippo's curved upper canines are oval to rounded in cross-section. In the uprocessed state, a deep longitudinal indentation extends for the length of the tooth on the inner surface of the curve. A broad longitudinal band of enamel covers approximately two-thirds of the surface area of the tooth. This enamel band is frequently removed during the carving process. The surface which is not coated with enamel displays a very thin layer of cementum. This may also be removed during processing. The interstitial zone in the upper canine is a curved line or broadly arched line.

hippo upper canine Click to see cross section of hippo upper canine

The lower canines are the hippo's largest teeth. They are strongly curved. In cross section, the lower canines are triangular. Raw lower canines will display a faint longitudinal indentation, a marked rippling of the surface and an approximately two-thirds coverage with enamel. Like the upper canine, a thin layer of cementum exists in the areas not covered with enamel. And, as with the upper canines , these surface characteristics are frequently removed during processing.

hippo lower canine Click to see cross section of hippo lower canine

Hippo incisors can be described as peg shaped. Enamel is found on the tooth crown. The center of the tooth in cross-section shows a small dot.

hippo incisor Click to see cross section of hippo incisor


WART HOG

(Phacochoerus aethiopicus)

Wart hog ivory comes from the animal's upper and lower canine teeth. These tusks are strongly curved and have generally squared cross-sections. Full length to near full length furrows and a longitudinal enamel band with approximately one-half to two-thirds coverage mark the tusk's surface in the raw, unprocessed state. The interstitial zone is a narrow line. Wart hog ivory tends to have a mottled appearance. Examination of a cross-section with a 10X hand lens reveals that wart hog dentine shows irregularly spaced concentric lines of varying thicknesses.

Warthog ivory Click to see cross section of wart hog tusk

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