Guaiacum Officinale (Lignum vitae)
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Lignum vitae, also known as guayacan or guaiacum, and in Europe referred to as Pockholz or pokhout, is a wood sourced from trees of the genus Guaiacum. These trees are native to the Caribbean and the northern coast of South America, including countries like Colombia and Venezuela. Since the early 16th century, lignum vitae has been a significant export to Europe, valued for its exceptional strength, toughness, and density. It also holds cultural significance as the national tree of the Bahamas and the Jamaican national flower.

The wood mainly comes from Guaiacum officinale and Guaiacum sanctum, which are small and slow-growing trees. Today, all species of Guaiacum are listed in Appendix II of CITES due to concerns about their conservation status, with G. sanctum specifically categorized as Near Threatened by the IUCN Red List. Advances in materials science have decreased the demand for lignum vitae, as modern polymers, alloys, and composites can now fulfill many of the wood’s traditional roles.

It is important to distinguish genuine lignum vitae from other hardwoods that may be called by the same name. Notably, woods from Bulnesia arborea and Bulnesia sarmientoi, now reclassified as Plectrocarpa arborea and Plectrocarpa sarmientoi, are known as verawood or Argentine lignum vitae and share some similarities with the true lignum vitae. Additionally, some hardwoods from Australasia, such as Vitex lignum-vitae and certain species of Acacia and Eucalyptus, are also referred to as lignum vitae.

Names
Lignum vitae, which translates from Latin as "wood of life," is named for its medicinal properties. The resin of this wood has been used to treat a range of conditions, from coughs to arthritis.

It is also known by other names such as palo santo, meaning "holy wood" in Spanish, and Aura palo santo. The term "bastard greenheart" is used as well, though it should not be confused with true greenheart (Chlorocardium rodiei), which is a distinct wood used in shipbuilding and cabinetry. Additionally, lignum vitae is one of several hard, dense woods often referred to as "ironwood."

Wood products
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Lignum vitae is renowned for its hardness and durability, making it one of the densest woods available, with an average dried density around 79 lb/ft³ or 1,260 kg/m³. This high density causes it to sink in water. It is the hardest of the commercially traded woods, according to the Janka hardness scale, where it achieves a hardness rating of 4,500 lbf. This surpasses other hard woods like Olneya, African blackwood, and hickory. While Allocasuarina luehmannii is noted for having an even higher density, lignum vitae remains a standout for its exceptional qualities in various applications.

Uses
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Lignum vitae's exceptional density and durability make it ideal for a variety of specialized uses. Its weight makes it suitable for manufacturing cricket bails, especially "heavy bails" used in windy conditions. Additionally, it is used to make lawn bowls, croquet mallets, and skittles balls. Historically, lignum vitae was widely utilized in making mortars, pestles, and wood carvers' mallets.

It was traditionally used for British police truncheons due to its density and strength, which allowed it to bruise or stun rather than cut the skin, offering a practical alternative to metal.

On sailing ships such as the USS Constitution, lignum vitae was used for belaying pins and deadeyes. The wood’s natural oils and density helped it withstand marine weathering and resist jamming in mortise holes. It was also used in the sheaves of blocks until modern synthetic materials became available.

The toughness of lignum vitae made it suitable as a lap in gem cutting, where it was covered with powdered industrial diamond to smooth rough gem surfaces.

Master clockmaker John Harrison used lignum vitae in the bearings and gears of his pendulum clocks and marine chronometers. The wood's self-lubricating properties eliminated the need for horological oils, which could become viscous and affect timepiece accuracy under adverse conditions.

In maritime and hydroelectric applications, lignum vitae was employed in water-lubricated shaft bearings and stern-tube bearings for ship propeller shafts until the 1960s, when sealed white metal bearings became common. Its use extended to the shaft bearings of WWII submarines and early nuclear submarines, as well as hydroelectric plant turbines, with some bearings still in service.

During the early 20th century, lignum vitae was used in the construction of insulators for San Francisco’s trolley system due to its ability to withstand high stress and temperature. Many of these insulators remained in use until the 1970s, and the last of them were replaced by underground systems in the 2000s.

Additionally, lignum vitae was extensively used in British Railways Mark 1 rolling stock as bump stops in bogies, the frames that support the wheels.