Experiments with Tagua nuts.
To find out how vegetable ivory would work for clock parts, I tried making a few parts and have noted my findings.
Vegetable ivory from South America cuts very freely with a hacksaw and turns readily in a lathe. Cutting a pinion with a CNC miller (1.2mm end mill, 20,000RPM, 100 inches per minute feed and 2mm depth of cut) resulted in the tool getting blocked and snapping off - I think that the form needs to be rough cut to eliminat blocking.
The coefficient of friction between two blocks of vegetable ivory seemed to be very low, not discernably different from PTFE on PTFE, better than nylon on nylon or any two woods and hugely better than acrylic on acrylic. (all tests subjective by hand rubbing of finely sanded blocks.)
It seems quite hard - though I think that vegetable ivory from Africa is harder but has less usable material. The biggest problem seems to be the cracks which radiate from the inner void which make the biggest part something like a 20mm dia by 8mm thick pinion.
On stability, I don't know yet but I have cut a bunch of blocks and measured them accurately. I will check them over the next few years.
Appearance: super white - a lot like genuine PTFE or maybe Nylon. I think it the surface turns brown over a period of years.