The subject says it all. Could a core sample from a few thousand feet below ground be turned into a pen in some fashion we can do ourselves, our am I going to need to find a laser lathe or something?
Well, a little imagination can go a long way and I can't see why you couldn't do a pen out of a rock sample using most of the traditional pen making tools, there is, is perfectly possible to cut the core and drill it to great precision and ease, simply using a diamond disc on a 4" grinder and a masonry drill bit one on many types available to everyone,
here is a good example of simple tools you can use with that type of materials...!
Putting the drilled and tubed piece on a normal mandrel, using the 4" diamond grinding disc to get it to size and shape and then using the "Flap" stone (blue) discs on the same 4" grinder, you can "easily" turn your core sample to the pen type and shape you desire.
Polishing stone is not much difference than a normal friction polish and nothing will stop you to finish it with the CA method...!
No need for sophisticated equipment, just some "inexpensive" diamond tools/finishers, a good dusk musk, some clean water and lots of patience, will produce very good results, after all, is there any material in existence that hasn't been used to pen making with great success, the one way or the other...??? I think not...!
Good luck...!
Cheers
George