This is in the image/banner for the Gem Digger Achievement and this item exists:

But what is a Dream Gem?

They got renamed and reimaged to [item2=dream coda caves crystal] So no there's no item that looks like that on-site anymore. Just like the current item, you'd get them from digging in the Coda Caves which are open right now.

Shame. It would've looked great in Kindergartner's TC.