has anyone worked with shells before?

[pomegranite.livejournal.com]

I'm working with some sea shells to make jewelry and some of the shells are very thin and delicate and seem to be in layers of an irridecent material. My problem is where I have drilled the hole for the jump ring etc. seems to want to peel and break. Does anyone have any ideas on how I might be able to strengthen them? I'm thinking of using some poly-acrylic or something?

I apologize that I do not have pictures, I know it would help.