Heaven gems?

Hi everyone, I started to play this game some days ago and I'm really loving it.
More then the usual grinding I'm really enjoying the crafting and farming for resources but this also mean that I really need more storage space!
So I started to build some furniture but I can't place in my heaven bag, probably because I need these... gems things but I really have no idea how to obtain them and the wiki didn't really helped.
It always feel like a waste to delete resources and selling to other player is such a slow thing that the deleting is usually the only option now.

Long story short how do I get the heaven gems?