Photo of Ivory in Processed & Rough Form
Ivory is a mineral with a hardness of 3 out of 10 on the Mohs scale of mineral hardness [?]. These Amorphously structured gems are made of calcium hydroxyphosphate, their full chemical compound being Ca5(PO4)3(OH).
Ivory is an organic gem material, largely obtained from the tusks of African and Indian (Asiatic) elephants, but also from the teeth and 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 carbonate, bound together by large amounts of the proteinaceous organic substance dentine, to form a compact, elastic, tenacious whole.
Tusks are the continuously-growing incisors of the elephant, and 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.
Its color, off-white with a faint yellow tinge, turns yellower with age. Aging sometimes produces small cracks, mostly lengthwise, probably due to dehydration and alteration of the organic substance.
Its longitudinal grain is always 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 the cross section.
Ivory's low level of hardness 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.
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 millimeters or a little more (as in the slats of ladies' handheld fans), it is fairly elastic. It is tenacious without any tendency to splinter.
Most ivory comes from elephants, particularly the African elephant which lives mainly on the savannahs. Cameroon, Gabon, Zaire, Ghana, Sierra Leone, Tanzania, and Mozambique are particularly rich in ivory.
Ivory also comes from Burma, Thailand, and other parts of Southeast Asia.
Other organic gem materials are horn, bone, coral, jet, pearl, and amber.
The specific gravity [?] for Ivory is 1.9, its refractive index [?] is 1.53-1.54, and its double refraction [?] is None.
History
Ivory comes from the Latin name for it, "ebur." The zenith of its popularity was probably around the thirteenth century both in Europe and China, despite their completely different cultures.
The fossil ivory used in Ancient China apparently came from Siberia and perhaps China as well.
Tusks of the male African elephant, the main source of ivory, 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.
Industrial Usages
Ivory 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 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.
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.
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 been mainly used for sculptures, boxes, and containers with bas-relief decorations, elaborate weapon handles, fans, and even inlays for furniture.
Plastic imitations of ivory, have, at the most, 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 any type of plastic.
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