Guayacan (Guaiacum officinale) is quite famous for being "the densest wood in the world" — it ranks among the top of the "Janka Scale of Hardness," which measures such things. The wood is also believed to have medicinal properties in its resins and chips; "Lignum Vitae" is, after all, Latin for "Wood of Life."

Unfortunately, because of Genuine Lignum Vitae's highly desirable properties, the wood has been grossly over harvested and is now practically on the endangered species list (which, of course, is sadly ironic, considering the meaning of its name). Although some Genuine Lignum Vitae is still available on the market, it is no longer being sold in any significant quantities.