All right, so if the final step of the process seems worth messing with at all - if they're losing spellsilver from it, or it's finicky, or doing things with the bone to make whatever ingredients gets used is otherwise expensive - try burning seashells to ash and using the ash. That'll get you a purer version of one underlying component of bone that Keltham would guess to be more likely the important one of the two. Better yet would be 'limestone' but Keltham doesn't remember off the top of the head how to describe which kind of rock that is, short of testing out different kinds of rock to see which ones behave chemically like 'limestone' should.
People have occasionally talked like spellsilver gets depleted in the process of making magic items. How does depleted spellsilver differ from the non-depleted sort?
