What the name covers
The trees and shrubs behind the name have wood of exceptionally high hardness, dry density and resistance to mechanical wear. Such woods generally sink in water rather than float. These unrelated hardwoods come mostly from subtropical and tropical regions. Most ironwoods are very well suited for woodturning on a lathe. The name is frequently used in the commercial terminology of the timber trade.
Woods called ironwood
Eusideroxylon zwageri is commonly known as Bornean ironwood, or by the Malay names belian and ulin. Olneya tesota is commonly known as ironwood, desert ironwood or palo fierro in Spanish. Lignum vitae is also one of the numerous hard, dense woods loosely referred to as ironwood. On the Janka scale of hardness, lignum vitae ranks highest of the trade woods, with a hardness of 4,390 lbf.
Bornean ironwood
Bornean ironwood is predominantly found in Borneo and Sumatra, where it grows in lowland rainforests, but may also occur in the Philippines. The tree is extremely slow growing, reaching up to 50 metres in height, with trunks over 2 metres in diameter. Carbon dating of timber segments from 15 logged stumps in Kubah National Park found that the species can live more than 1000 years.
Ulin is one of the heaviest and most durable timbers of South-East Asia. The heartwood is yellowish-brown to reddish-brown when freshly cut, but it becomes silvery brown, dark brown or almost black on exposure. Ulin is preferably used in marine constructions such as pilings, wharfs, docks, sluices, dams and ships. It is also used for the traditional houses, called longhouses, of the Dayak in Borneo. Roof shingles of ulin are reported to last 50 years to more than a century.
Ulin wood contains 58% cellulose, 29% lignin, 12.5% pentosan, 1.0% ash and up to 0.5% silica. Extract of ulin wood, described as essential oils, may be a promising source of antioxidants and termite control substances.
Desert ironwood
Olneya tesota is part of the western Sonoran Desert in Mexico and the United States. Olneya ironwood is very hard and heavy, and because its density is greater than that of water it sinks. Most of its commercial uses are artisanal, such as durable wooden sculptures and knife handles. Ironwood Forest National Monument in south-central Arizona is named for O. tesota.
Lignum vitae
Guaiacum officinale is one of two species yielding the true lignum vitae, the other being Guaiacum sanctum. Lignum vitae is sometimes used to make lawn bowls, croquet mallets and skittles balls. The trade of all species of Guaiacum is controlled under CITES Appendix II.
Oil of guaiac and guaiol
Oil of guaiac is a yellow to greenish yellow semi-solid mass which melts around 40-50 °C. Guaiol, also called champacol, is a sesquiterpenoid alcohol found in several plants, especially in the oil of guaiacum and cypress pine. Its formula is C₁₅H₂₆O and its molar mass is 222.372 g/mol. Guaiol is a crystalline solid that melts at 92 °C.
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Related: Alder · Alpha Humulene · Amaranth · Amberever · Amburana Bark · Antillone · Apple Tree
