Here there is a crystal I did see how it could look like in marmoset. It is far from perfection, but I did it thinking about doing a fantasy asset, as the big crystal in Final Fantasy Crystal Chronicle (that after checking, is way more realistic :p ) Critics are welcome.
Here is a crystal typ of strange rock , I've started in Max with a simple vorino fragmentation and then some scraping mudbox Viewer: https://www.artstation.com/artwork/6vENn