I just wanted to confirm this before I did anything, and the Zam page for these items doesn't have the "Currency For" tab yet. :)
The blue and purple shards you get from major zone events are zone specific, and you should spend spend spend them before you go to the next zone, yes?
I'd been saving them up, but then when I moved from Silverwood to Gloamwood (OMG COOLEST ZONE EVAR!) I noticed I got a completely different shard.