What do you need?
Two large half-shells
glue and a brush
glitter powder
a pearl (bead)
varnish and brush
This glittering shell with a pearl inside matches the shell crystals. Use the left over half shell with Alum from when you made the crystals.
Brush glue on the outside of the first half shell.
Sprinkle glitter powder over the glue, let it dry.
Brush glue on the inside of the second half shell.
Spread the glue with a brush into the corners.
Sprinkle glitter powder on the glue and let the glue dry.
Press a pearl (bead) in the middle of the shell into the wet glue.
Varnish over the glitter on the inside and the outside so it won't come off.
Keep the shell with the crystals, then the whole 'treasure' stays together.
The crystals sparkle beautiful in sunschine but if you leave them to long in the sun they fade.