You know what'd be awesome? Imagine, in hot, wet, dangerous Biomes, you could find huge, dramatic crystal caves if you dug deep enough.
They'd be large, cavernous rooms with pillars of gypsum jutting from the ceiling and walls. Many ores could be found, too. But the extreme heat and clouds of poison gas would limit your trips to about 3 minutes a piece.
I'd imagine the Gypsum blocks would be slightly transparent, shiny looking crystals. The pillar blocks would be smooth and gleaming, and the wall and floor crystals would be knubby and slightly glimmery.