Great class as usual, Yasmina! I'm really digging this topic; trying to get that luminescence in the crystal is pretty challenging!
I've just been doodling with some colored pencils and explored a bit using white india ink. I'd like to try watercolors and even some digital versions. Here's a couple of the sketches I did today:
Edit: Did some digital versions of some crystals. I'll be trying some watercolor studies this week as well, I'll update soon. :)