Teak (Tectona grandis), one of the most valuable timbers known, is the wood of a large deciduous tree (natural order Verbenaceæ) with leaves from 10 to 20 inches in length, and from 8 to 15 inches in breadth. The tree, which has small white flowers in panicles, is found in Central and Southern India, where, however, it is now scarce in some localities in which it was formerly plentiful. There are extensive forests of it in Burma and Siam, and it extends into Java and some neighbouring islands. In India growing teak is placed under the management of a conservator of forests, and very little is now exported from that country. The wood is of a quiet yellow colour, tending to brown, and like many other kinds of timber has a characteristic odour. It is classed as a hardwood, though it is only of medium hardness, taking, however, a good polish; and it is straight grained and strong. Although easily worked when not long cut down, it readily blunts tools after being kept some length of time. Its average specific gravity when dry is about 535. Teak does not shrink much in seasoning, and it is believed to expand and contract less by differences of temperature than most woods. Unless very thoroughly seasoned it has some tendency to split, and this is perhaps its chief defect. It is much less resinous than some other well-known hardwoods, such as mahogany and rosewood, but it is usually said to contain an aromatic essential oil which prevents iron in contact with it from becoming rusted, and for this reason it is always used for the backing to the armour-plates of ships of war. A sticky elastic extract, to some extent resembling india-rubber, is obtained from teak by treating the wood with naphtha or ether. It is probably this which is the real cause of the wood preventing iron from rusting. The pores of the wood are sometimes filled with a white substance, which has been ascertained to be phosphate of lime (calcium phosphate). There is a high percentage both of this substance and of silica in the ash of teak, and this no doubt explains why carpenters and other tradesmen consider it gritty. White ants rarely attack the wood if it is sound, but nevertheless logs of it are often badly worm-eaten; these, however, are rarely sent to Europe, and are believed to be derived from unhealthy trees. Teak wood varies considerably in quality even when perfectly sound.
In India teak is used for all kinds of work where strength and durability are required, such as for building ships, houses, and bridges; also for the construction of railway carriages and furniture. In England it is largely employed in shipbuilding, and to some extent for architectural purposes, such as shop fronts, as well as for furniture. It has numerous minor applications. The leaves of the tree yield a red dye. Being of large size they are used in India for plates and for thatching. The great increase in the consumption of teak in recent years shows that the wood is much appreciated for its valuable properties. In 1890 the imports into Great Britain were 60,182 loads, value £680,162; while in 1880 they only amounted to 33,800 loads.
African teak (Oldfieldia Africana) is imported from the west coast of Africa; it is also a valuable timber, but less so than true teak.