This material is largely obtained from the tusks of African and Indian (Asiatic) elephants, but also from the teeth or tusks of the hippopotamus, walrus, and other mammals. Like bones, it consists mainly of calcium phosphate in the form of oxyapatite and a small quantity of calcium carbon-ate, bound together by large amounts of the proteinaceous organic substance dentine to form a compact, elastic, tenacious whole.
Tusks, which are the continuously growing incisors of the elephant, have a very long, slightly curved, roughly conical shape with an internal cavity which is also conical, petering out part-way along. When viewed in cross-section, the organic structure displays thin, slightly translucent, intersecting curved lines, similar to the marks left on a flat surface by a milling machine. The color off-white with a faint yellow tinge, turns yellower with age. Aging sometimes also produces small cracks, mostly lengthwise, probably due to dehydration and alteration of the organic substance. The tusks of the male African elephant average two meters in length and may weigh 30 to 40 kg; those of the Asiatic elephant are somewhat small and less heavy. Much of the ivory formerly used in China came from fossil remains of mammoths, with very large, strongly curved tusks which were well preserved and still perfectly workable.
The hardness of 2.50 2.75 makes it fairly easy to fashion with ordinary metal tools. It also has considerable elasticity and tenacity, with the result that ivory objects are very strong and durable. The average density is about 1.79-1.80 g/cm3. It is hard to measure the refractive index, because of its lack of transparency, but this is normally about 1.53 or 1.54.
As mentioned, it is of organic origin, being the typical material of mammals' teeth.
Most ivory comes from elephants, particularly the African elephant which lives mairoy on the savannahs. Cameroon, Gabon, Zaire, Ghana. Sierra Leone, Tanzania, and Mozambique are thus particularly rich in ivory. Ivory also comes from India, Burma, Thailand, and other parts of Southeast Asia. The fossil ivory used in ancient China apparently came from Siberia and perhaps China as well.
The name comes from the Latin ebur, of identical meaning. It has always been used as an ornamental material, but at various times over the centuries was much more highly prized than it is today. The zenith of its popularity was probably around the thirteenth century strangely, both in Europe and in China, despite their completely different cultures.
The cream to yellowish white color is characteristic (and is in fact known as ivory color); it turns a drab yellow-brown with age. The longitudinal grain is al-ways visible in bright light, due to the difference in translucence between one part of the tusk and another, and this displays the distinctive pattern of intersecting curves In cross section. It easily takes a good polish, although more crudely worked pieces (e.g., some low quality African craft objects) may display scratch marks from the planes used to fashion them. In thicknesses of a millimeter or a little more (as in the slats of some cooling fans as used by ladies) it is fairly elastic. It is tenacious without any tendency to splinter. The ornaments and luxury items, past and present, made of ivory are too numerous to mention. They include round-beaded necklaces and bangles, easily produced from the hollow basal portion of the tusk; carved pieces in bas-relief, for use both as pendant jewelry and the outer panels, for instance, of boxes and containers, and ceremonial weapon handles. Sculptures of human figures are also common. In Africa especially, entire tusks are carved without interfering with their basic shape and size, the completed piece designed to stand upright. Complete tusks are also fashioned in China, Japan, and India, but these are normally intended to be viewed horizontally and depict landscapes or everyday scenes, with an abundance of vegetation, houses, and pagodas, shown in minute de-tail. Small sculptures or other objects are also put together from numerous, juxtaposed pieces of ivory fixed to a thin wooden support, not visible in the finished article. This produces works of art exceeding the size of a single tusk and having the appearance of single-color "mosaics. Oriental art forms also include complex-shaped containers, with minutely worked, carved walls and intricately pierced details. In the West, ivory has mainly been used for sculptures, boxes, and containers with bas-relief decorations, elaborate weapon handles, fans, and even inlays for furniture.
Ivory's chief characteristic is its line grain, distinguished from the background only by a slight increase in translucency, best seen in strong light, al-though barely visible, if at all, on the natural outer surface of the tusks, where this has been preserved. This readily distinguishes it from bone, which has a heterogeneous network of markings, although this is only visible under a microscope. Plastic imitations of ivory have, at the most, thin superficial furrows which crudely imitate the longitudinal grain and these melt and scorch visibly if touched with the tip of a thin piece of red-hot wire. Ivory also turns black and gives off a smell of burning protein when burned, but the prevalence of the organic component gives it far greater resistance than aley type of plastic. If necessary, measurement of the density is also very useful for distinguishing ivory from its imitations.
As mentioned above, most ivory comes from various parts of Africa (mainly Cameroon, Gabon, Zaire, Ghana, Sierra Leone, Angola, Tanzania, Mozambique, and Zimbabwe) and Asia (mainly India, Thailand, and Burma).
The price of ivory has risen again recently, but as with jade, very much depends on the quality of the workmanship, which can be outstanding because of the intrinsic qualities of the material. When the workmanship is excel-lent, the value of ivory may equal that of other prized ornamental materials, including jade. But when the work is more commonplace, its value is much lower, although it will Still be higher than that of small, mass-produced objects in, say, nephrite jade.
Ivory was and is widely imitated by all types of plastics. Among the moulded objects produced are some which are far too large to have come from a single piece of ivory, as for instance, small tables with a carved central pedestal. Sometimes, complete carved tusks have been made out of these plastics, which are very hard to distinguish from the real thing, at least with the naked eye. Many umbrella and walking-stick handles made earlier in the twentieth century are also of plastic, as are dressing table sets of the same period. All these imitations generally have a lower density than that of ivory, but much higher than that of transparent plastics, inert mineral powders having been incorporated in them to add to their credibility.
Writer – Curzio Cipriani & Alessandro Borelli