What to do with certain collectables

[Brennus]

I'd gathered a bunch of Ice Stalagmites for Zoe Aliapoh, and apparently past a certain point she doesn't accept them any longer. What to do with them? Can't sell them, is discarding them the only solution?

I looked around for info on this but can't seem to find it anywhere, thanks for any advice.

[Jojoya]

There's a random chance that Ice Stalagmites will show up as the weekly delivery in the future. Once you hit max rank, the requested delivery each week will randomly change between all the possible deliveries.

Discarding them is your best option at this point. They're taking up inventory space and easy to gather again if you do ever need them.