Here at Long Now we are now experimenting with new ways of using stone in the Clock after being introduced to Stuart Kendall and Jason Clausen, the stone crafters of Seattle Solstice. They have built new machines to cut stone in ways not before possible. Their work in large stone is machined to tolerances usually only associated with metalwork. Above you can see one of the test gears being cut by their custom computer controlled diamond wire saw.
The point of using stone in the 10,000 Year Clock is to isolate metal to metal contact. This prevents one of the most potentially destructive effects in the Clock, galvanic corrosion, which occurs between dissimilar metals. We are trying the stone in accelerated load test rigs (seen above) against other materials we might use in the Clock. While at first we thought that machining jade like this was quite original, it turns out that it may have been one of the earliest substances machined.
Stuart Kendall suggested that if we wanted to build working clock parts of stone, we should try nephrite jade. A type of stone that is very hard, polishes well, and has one of the highest tensile strengths of any stone (more like metal in fact). We are beginning to test parts made of nephrite jade now. Below you can see one of the roller test rigs that has made over 4 million revolutions against another jade roller and against a stainless roller. So far it is performing well.
