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Ebony

species black wood density

Ebony (Diospyros spp., family Ebenaceae) are species of tropical hardwood trees favored for their hard and beautiful wood. Only the black or brown heartwood is used commercially. There are more than 300 species of ebony, ranging in size from shrubs to trees taller than 100 ft (30 m). The best commercial ebony comes from India, Madagascar, Nigeria, Zaire, and the Celebes Islands. Most species of ebony are found in the tropics, but some are found in warm temperate zones. The latter includes the American persimmon (Diospyrus virginiana), whose heartwood is not a full black and does not have the extreme density that is so desirable for carving and fine woodwork. Aggressive harvesting of ebony has rendered many species of ebony rare and endangered, and consequently, quite valuable.

Plants in the Ebenaceae family have simple, alternate, coriaceous (or leathery) leaves that are oblong or lanceolate, and vary in length according to species. The flowers are white or greenish-white, with at least four stamens. The globular fruits are sought by animals and humans alike because of their sweetness when ripe. Some indigenous tribes use the fruit to make beer. The leaves and other parts of the tree are used in traditional medicine to treat intestinal parasites, wounds, dysentery, and fever, but laboratory tests have not verified the efficacy of this medicinal usage.

The wood of the ebony is so dense, it rapidly dulls tools used for working, sawing, or turning it. Even termites will bypass a fallen ebony log. This density contributes to ebony's commercial appeal, as it results in a finish that will take a high polish, adding to its beauty. The properties, attributed to ebony through both fact and myth, have been recognized for many generations. It has long been a favorite material for carving in Africa. Some rulers in India had scepters made from it, and also used it for their drinking vessels as it was believed to neutralize poisons. Today, ebony is used for many purposes, including tool and knife handles, furniture, inlay work, wall paneling, golf club heads, and musical instruments. For many years ebony was used for the black keys on the piano, but increasing costs have necessitated the use of synthetic substitutes. Today, only the most expensive concert pianos are still made with ebony. Ebony is also used in stringed instruments for tension pegs and fingerboards.

Although there are many species of ebony, only a few provide commercial-grade wood, and the demand far exceeds the supply. Africa is the source of the most desirable, jet-black heartwood. It comes from the species Diospyrus crassiflora, commonly called African ebony. This ebony is prized for its intensely black core. With a wood-density of 64 lb/cu. ft (1,030 kg/cu. m), it has a specific gravity of 1.03 and will not float in water. It is found in Cameroon, Ghana, Nigeria, and Zaire.

Diospyrus macassar, commonly called Macassar ebony, is not as plentiful as the African species, but its greater density makes it even more useful in certain types of manufacturing. With a weight of 68 lb/cu ft (1,090 kg/cu m), it is even more dense than African ebony. It has a specific gravity of 1.09, and also does not float. Macassar ebony is found mostly in the Celebes Islands of Indonesia, with some minor growth in India. The heartwood is frequently streaked with lighter bands, and this type is favored by piano makers. Because they are so difficult to dry, the trees are usually girdled to kill them and then left standing for two years to dry out. After they are felled and cut into lumber, they must dry for another six months.

Diospyros mespiliformis, also known as the Jakkals-bessie (Jackal's berry), Transvaal ebony, or Rhodesian ebony, is a straight tree that grows 70 ft (21 m) tall with a trunk up to 4 ft (1.4 m) or more in diameter. It is more widespread and abundant than other ebonies, but the heartwood is more brown than black, limiting its appeal. Among many native cultures, it serves a medicinal purpose and concoctions derived from the leaves and bark are used to treat wounds, fevers, and intestinal parasites. Color aside, the density of Rhodesian ebony renders it desirable for furniture, knife handles, and flooring. The fruit is edible.

Diospyrus virginiana, the persimmon, or American ebony, is a native of the southeastern United States. It takes approximately 100 years to mature and grows to a height of 65 ft (20 m). Like the tropical ebonies, it has simple, alternate coriaceous leaves. The flowers are yellowish green and the fruit is yellow, globose, and somewhat larger than its tropical cousins (up to 2.5 in [6.4 cm] in diameter). The fruits are filled with many seeds and have a sweet, custard-like interior. Due to its hardness, the wood is used for handles, furniture, and golf club heads. Since there are no vast groves of persimmon, it is not of great economic importance. Persimmon weighs 53–55 lb/cu ft (826–904 kg/cu m).

The growing scarcity of all types of commercial ebony has steadily increased its value. All commercially valuable species are becoming rare, and some are endangered in their wild habitats. Many of the uses of ebony can be substituted by synthetic materials, such as hard plastics, although these do not have the aesthetic appeal of true ebony wood.

Resources

Books

Dale, Ivan R. Kenya Trees and Shrubs. London: Hatchards, 1991.


J. Gordon Miller

KEY TERMS

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Calyx

—All the sepals of a flower, collectively.

Coriaceous

—Leathery in texture, thicker than normal.

Dioecious

—Plants in which male and female flowers occur on separate plants.

Lanceolate

—Lance shaped.

Sepals

—Usually outermost division of the calyx.

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over 5 years ago

There is a tree called in Luo, "Powo" or slea solesticus: does it exist?

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