Shell drilling suggestions?

[chennpug.livejournal.com]

I just got back from a trip where I collected some bits and pieces of seashells, sea glass, etc, and I'd like to incorporate some of the pieces into a windchime/mobile. However, as some of the pieces are very hard and some are fragile, I'm not sure what to use to bore holes with, so that I can tie them up.

Any suggestions, or resources I might look at?