That is one pretty chunk of amboyna!!! WOW!!!
If you decide with pen blanks, I'll chime with the guys...save the natural edge for now. You won't get much from them but may be of other uses later (like a desk set or other stuff).
If it is for your own use...do not cut them to length yet. On a 16" long bar, you may get 4 pens if you just cut the exact blank length you need. You won't believe how much waste (% wise) we produce from 5.5" to 6" long blanks.
If it is no secret...how much did this chunk cost you?