>>169813661> Their shells still exist
Don't we see one of the slugs on the surface? And Ventricosus implies that most of her people are living on the moon, so I doubt there would be a shortage of shells around.> And not synthetic gems
Even if it were, they would be able to find out pretty easily by checking whether there were inclusions or not, and then just keep going.
Both races are immortal, and while the spirits just want to be able to pass on, it would make sense for them to at least make sure that this method works and that they can get viable shards out of the slugs before they do so. As it is, I can see why the spirits would want the gems to get what they want, since they're basically the only ones who could potentially fix Adamant, since they've already tried everything they could think of.