This is a supplemental companion guide to the USFWS Ivory Guide.
Ivory is the dentine portion of a mammal’s tooth. A tusk is a tooth that remains outside of the animal when its mouth is shut.
There is only one way to determine if an object is ivory, and if so, what type. It’s not the so called “hot needle” test (there is no such thing), it’s learning the gross morphology of each tooth and tusk. In simple terms this means learning and remembering the size, shape, internal structure, and grain pattern of each type, so that you can look for traces of them in a processed carving.
All teeth have a pulp hollow where the tooth grows, a dentine section, a cementum layer that helps it adhere to the gums (sometimes called the bark or rind), and in some but not all cases a final protective layer of enamel.
ELEPHANT FAMILY- There are characteristics common to the living elephants, mammoths, and paleomastodon that make the ivory component of their incisor tusks similar to each other, but different from all other types of ivory.
First of all their tusks are large, slightly curved, mostly round, hollow at the large end, with parallel wavy lines longitudinally, a nerve root that looks like a black round dot and extends from the end of the hollow to the tip, and they alone contain a grain patter seen in cross-section that looks like intersecting lines that form a diamond pattern. This is officially called the Schreger lines, but usually referred to as cross-hatching or engine turning. This pattern has never been successfully replicated in ivory substitutes.
The only differences between living elephant ivory and ivory recovered from long dead members of the family are that the mammoth and mastodon tusks often have absorbed coloration from the minerals where they were buried and that the angles of the Schreger lines differ. When measured with a protractor, the modern elephant ivory have angles measuring 100 degrees or greater while the extinct ivory measures under 100 degrees.
WALRUS- The second most common type of ivory is from the canine tusks of the walrus. The diagnostic characteristic of this ivory is the fact that the nerve hollow fills in with a crystalline-like structure called secondary dentine. There is no nerve root. The tusks are also more oval than elephant family tusks and often have a groove on the side. No other ivory has this crystalline structure, so if traces are seen in the finished carving the only possible conclusion is that it is walrus ivory.
HIPPOPOTOMUS- Hippos have three kinds of teeth that are used in ivory carvings, the upper and lower canines, and the incisors. The largest is the lower canine. Both canines are heavily curved, triangular in shape, but the upper canine has a deep groove on one side that in cross-section looks like a “heart” shape. The incisor is straighter and round in shape. There is a nerve root that looks like a “dash” or curved line properly referred to as a “TIZ”. The grain pattern is very fine and difficult to see. Radial cracks are common.
WHALES- There are only two members of the whale family that provide commercially useful teeth. They are the Sperm Whale and the rare Arctic Narwhal.
Sperm whales have up to 50 teeth (post canine) all in the lower jaw. They are cone-shaped with a hollow end and a nerve root that goes to the tip. The distinguishing characteristic is a clear line of transition between the dentine and cementum layers.
The narwhal has a long (up to 10’) incisor tusk that is mostly hollow and has a unique left-hand twist. No other tusk has this appearance, and since it is the rarest type of natural ivory, some portion of the twisted exterior is always left to be seen. In cross-section the grain patter follows the shape of the hollow and radial cracks are common.
Normally only the males have this tusk and it grows on the left side. There have been examples of males with two tusks and of females with a tusk, even one case of a female with two tusks. They were at one time thought to be the horn of a Unicorn.
PIG FAMILY- This group consists of three members, boar, warthog, and babirusa, however the babirusa is so rare as to almost never be seen.
Boar tusks are very similar to hippo tusks only smaller in size. They have upper and lower canines that are triangular in shape, and heavily curved. They can be carved but are usually used whole as handles or grips for cutlery, bottle openers, corkscrews, and such.
Warthog canines are four sided with a groove on three of the sides. They are heavily curved, and are also mostly used whole. They have a nerve root that in cross-section looks like a series of dots and is also referred to as a “TIZ”.