A Background to Ivories

A BACKGROUND TO IVORIES

IMPORTANT NOTICE: Ivory is an extremely emotive subject today. The majority of animals from which it is derived are threatened with extinction. It is, however, the view of Organic Gems that in order to help protect and save these animals, it is necessary to know what ivory is, and how to recognise it. The following is therefore not in any way intended as condoning the use of modern ivory, or the poaching of animals, but purely to educate.

Ivory derives from the teeth or tusks of many animals. Tusks are modified teeth -- they are larger and are still visible when the animal's mouth is closed. Ivories have been put to both decorative and utilitarian uses for thousands of years. The most famous ivory comes from the tusks of elephants, both Asian and African (both the males and females bear tusks in Africa, but only the male Asian elephants carry true tusks). Other ivory-bearing animals include walruses, hippopotamuses, various whales, members of the pig or suid family, and from the remains of mammoths.

The purpose of an animal’s teeth is obvious – they are for tearing or grinding up food whilst eating. The purpose of tusks is less obvious, and each animal has developed these oversized teeth for different reasons. Elephants use theirs to strip bark (food) from trees. Walruses use theirs to pull themselves up onto ice floes, and to trawl the sea bed. Many animals use their tusks for display (especially in the mating season), and for fighting.

WHAT IS IVORY?

Teeth consist mainly of dentine, a creamy-white, opaque material made up mainly of calcium phosphate, with some collagen. The dentine is covered in enamel which is very hard, and is often worn away by the animal through foraging and eating. Any enamel remaining on the tooth or tusk is usually removed before the material is carved. Cementum may also partially cover the dentine, and it holds the teeth or tusks in place in the animal’s jaw. Dentine, enamel and cementum all have a very similar colour.

The tusks of elephants, mammoths, walruses, hippos and whales are solid for much of their length. Those from the male narwhal (a small, arctic whale which usually carries a single, spiralling tusk that can measure over 2m in length), are hollow, and tusks from some of the suids, e.g. wild boar or warthog, may be hollow for much of their length.

RECOGNISING THE VARIOUS WORKED IVORIES

When worked, ivory has a high polish and a silky feel. The different ivories have characteristics that can enable us to recognise from which species they are derived. For example, when cut in cross section, elephant ivory displays a pattern of intersecting arcs commonly called the ‘engine turning’ pattern (and sometimes incorrectly called ‘lines of Retzius’). The term 'Schreger lines' can also be used. Viewed along its length, it has irregular, wavy lines.

Walrus ivory was used a lot in northern Europe in the Middle Ages as it was not possible to obtain elephant ivory. Also solid, it is the only ivory to have two distinct types of dentine, the outer displaying very fine concentric rings, and the inner a material that is best described as resembling milky rice pudding. This secondary dentine is as hard as the primary, but can be crumbly and is often avoided in carving. It is sometimes possible to find fossilised walrus ivory, and though it tends to be rather stained it has the same characteristic structure as new walrus ivory.

Left to right: cross sections of elephant tusk, mammoth tusk, walrus tusk, and section of narwhal tusk.

Narwhal ivory is often recognised by the fact that it is hollow and could therefore not be carved into solid figures. It was instead used in sections or small pieces, and sometimes whole as in walking canes or bishops’ crosiers. The outer surface of the ivory retains a diagonal pattern, even after polishing, caused by the spiral growth pattern. This material has been used predominantly in countries with access to, or trade around, the arctic seas.

Longitudinal section of sperm whale tooth showing thick layer of cementum, and detail of hippo ivory showing dense structure (measurements 1mm)

Sperm whale teeth, and those from the orca (also known as the killer whale), are much smaller and are peg-shaped. They are solid but have a fine, dark line running down the centre of the tooth, which sometimes shows in a carving. They also have a distinct line between the dentine and the cementum, a thick layer of which covers the tooth.

The tusks of animals in the suid family are not very large, and many are hollow. They are a triangular shape in cross-section, curved, and are not usually suitable for carving, but are sometimes used whole, with smaller examples strung together as bracelets. When encountered whole, the larger more solid tusks from these animals can be confused with the lower canines of the hippo which are also solid and curved, but which have a flattened, worn area at the tip where the tooth has rubbed against teeth in the upper jaw. Hippo ivory lacks distinguishing structural patterns, is very dense and is stain resistant.

Mammoth ivory resembles elephant ivory very closely. It is found in the permafrost in northern hemisphere, and is at least 4000 years old, usually more. Due to its age it is often cracked, and sometimes stained a brown colour. As some has been deep-frozen rather than fossilised, it can also occur as a very pale material and in good condition. In pieces and carvings that are large enough to show a section of the ‘engine turning’ pattern, it may be possible to detect that the intersecting arcs have a more acute angle than those of elephant ivory. This is most easily visible at the outer edge of the dentine.

IVORY& BONE, AND OTHER LOOKALIKES

The material most commonly confused with ivory is bone. It has the same colour and in small pieces it may not be possible to discern any structure. However, almost all bone is hollow and cannot therefore be carved into solid figures. To construct a sphere from bone (e.g. a bead), there must therefore be joins in the material. Also, bone has a characteristic totally lacking in ivories: tiny, nutrient-bearing canals, called Haversian canals. These appear as dark dots in cross-section, and as little lines along the length of the material.

Antler is a form of bone (and is a completely different material to horn). It also has Haversian canals, but it is often darker than bone, and it has a hard, finely-honeycombed centre. Only when this is cut away is it difficult to tell bone and antler apart. Reindeer antler is usually pale grey in colour.

Plastic is a popular imitation for ivory, but, unless a heavy filler has been added in manufacture, it lacks the weight and feel of the natural material. Early plastics used to imitate ivory were given various names such as Gallalith and Ivorine. Some of the imitations had no structural characteristics at all, whilst others attempted to imitate the engine turning pattern. In cross-section they appear as alternating dark and light areas rather than as intersecting arcs, and in longitudinal section these materials display distinct parallel lines, rather than the irregular wavy ones of elephant ivory.

Other fakes have been made from powdered, re-constituted bone. Although the weight and colour may be more convincing, there is a lack of structure in this material. Further, any material that has been constructed and moulded may show tell-tale signs, such as air bubbles or marks from the joins in the moulds. (See 'Early Plastics as Imitations of Organics'.)

Elephant ivory in longitudinal section, plastic imitating elephant ivory.

Left to right: elephant ivory box, bone box showing Haversian canals.

TESTS FOR IVORY

It can be almost impossible to tell exactly which type of ivory has been used to make an object, especially in small pieces, or roughly carved ones where the underlying structure is masked. It is more possibly important to know whether an item is ivory or bone, and this, too, can be difficult to ascertain in very small pieces, finely carved items, or furniture inlay.

A test that is sometimes carried out in a gem testing laboratory is to place the item under ultraviolet light to see whether it fluoresces. However, this test will not differentiate ivory from bone, as both fluoresce with a chalky white colour. Also casein, an early plastic that was used to imitate ivory, fluoresces in the same way. There are other, advanced tests using expensive equipment that can tell ivory from bone, and determine which species the ivory comes from. But in general, everyday practice, by far the best way to identify ivory is by sight.

WHERE TO SEE IVORIES

Ivory has been carved by mankind for 40,000 years, though very few ancient pieces survive as ivory is less durable than, for example, minerals.

There are beautiful collections of ivories in many museums world-wide, from the almost 3000 year old Assyrian ivory panels on show in New York, London and Bagdad, through the collections of medieval ivories in many European museums, to the later items such as dressing table sets of ivory-backed brushes which were popular in the twentieth century. Collections of Inuit artefacts always include arctic ivories, used as talismans, decoration, or utilitarian objects such as harpoon tips. Whaling museums on both sides of the Atlantic have collections of scrimshaw, which are items made from materials (including ivory) that have been derived from whales hunted for their oil, and carved, etched and decorated.

TRADE BANS

Ivory has been so widely used that most of the animals from which it derives are now under serious threat of extinction. This is especially true of the elephant which was killed purely for its tusks. Although whales are also under threat, their ivory has been a bi-product rather than the reason for their slaughter. As a result of the threat of extinction, there are now very strict ivory trade regulations or total bans in operation in the majority of countries.

There are exceptions to the bans, but these are complicated and the situation is ever-changing. Anyone wishing to purchase or sell ivory is advised to obtain up-to-date information from the appropriate local authorities, and to ensure that the correct documentation is present. If attempting to export or import ivories of any type, documentation needed will include proof of provenance, CITES (Convention on International Trade in Endangered Species) certificates, and export and import licences. All licenses and permits can take several weeks to obtain.