Lignum vitae is a very extraordinary timber from central America, the West Indies and northern South America, CITES protected now, thankfully. Extraordinary because of its properties of being immensely dense, highly water resistant, and containing a very waxy resin throughout its substance. https://en.wikipedia.org/wiki/Lignum_vitae
These properties led to its being used in numerous engineering and mechanical applications. It was, until the advent of modern alloys, polymers, and lubricants, commonly used for the ball bearings around ship propellor shafts, and other applications where its friction reduction properties, density and water resistance, were invaluable. Its properties, plus its extreme smoothness (when worked with very sharp tools), and the resulting waxy surfaces, were unique and useful, which led to its over-exploitation. Lawn bowling balls also used to be made from lignum vitae. A few years ago I purchased some ancient lignum vitae bowling balls through eBay, and have turned some of them into mallets for my use. They pack a lot of punch because of lignum vitae’s extreme density. A friend gave me a while back a fine lignum vitae bowling bowl he had found in the River Cam in Cambridge some years ago. His son is becoming a talented stringed musical instrument maker and whilst making my friend a cane head from cocus wood we talked about making his son a lignum vitae mallet, like mine. Mallets are an important bit of kit for woodworkers. They do not have to be lignum vitae, obviously, but one thing is certain, one made from lignum vitae will be extremely durable. Now completed, a new lignum vitae mallet, with an oak shaft, for a budding woodworker. Truly amazing stuff to turn on a lathe.