Lignum vitae is the common name for trees in the genus Guaiacum, and particularly for the heartwood of these trees, which is one of the densest and strongest woods in the world. These woods are also included under the expansive category of ironwood, a name often given to woods that are dense enough to sink in water.
Lignum vitae is Latin for 'wood of life', named so because of the medicines that early New World explorers claimed could be derived from its sap, gum, and tea made from wood chips. Unfortunately, the primary use was an imagined cure for syphilis; in fact lignum vitae only treats the rashes and sores that syphilis produces.
Historically, lignum vitae was the wood of choice for pretty much everything, despite being hard to work with, dulling cutters, and being resistant to glue. It was used for professional tools of all sorts, from plumber's turnpins to saddlemaker's mashers -- and until recently, the British police truncheons. The rich wanted decorative boxes made from lignum vitae, and the industrial barons wanted their railway ties made from lignum vitae. Due to its high natural oil content, it is water resistant and requires little or no lubrication, and so it was a popular choice for the fixtures on sailing ships (blocks, belaying pins, deadeyes, etc.). It was also in use for shaft bearings, trolley cord insulators (high voltage, high wear wire guides), and other industrial uses.
These trees have been a major export of the Caribbean and South America since the 1500s, and all five species of lignum vitae are currently listed as 'potentially endangered' species. Modern material science has provided many substitutes for lignum vitae, and it is no longer being harvested at a dangerous rate, but habitat loss is an increasing risk.