just to expand on AGM's fine info. lignum vitae is/was used in stern tube bearing & seals around the hull penetration of large low speed ship's propeller shafts. the seals used a trickle of water to lubricate and cool the wood bearing. lignum vitae essentially doesn't absorb water and is very hard and wear eresistant in this service. it also is denser than water (it sinks) and is not only expensive, but hard to find any more, the true LV is an endangered species, but small chunks for gun grips and knife handles can be found. wear a dust mask if you DIY (LV has medicinal uses when powdered). i used to see a lot of it around ship yards in sea ports as the wood was installed in dovetailed strips and needed replacement every decade or so. that source has dried up. modern seals are mechanical oil seals. great when they work, but a horror if they leak.
LV also makes nice clubs and walking sticks.
and it looks really cool polished up. also traditional for carver's mallets, marlin spikes, gavels, lawn bowls, wooden jars, etc.