I don't think I've ever seen any of this and I'm sure I don't want to! The rock is pretty, no doubt. but because of the possible side effects I think I'll pass!
The only thing worse than arsenic itself could be a rock made from arsenic and sulfur. The lethal and chemically reactive orpiment crystals are found growing below the surface in mineral formations, often near hydrothermal vents. The colors are seductive, but holding the crystals in your hands may release carcinogenic, neurotoxic arsenic powder. Like cinnabar, the Chinese made extensive use of this mineral, but to far more terrifying ends. Arrows would be rubbed on crushed samples of these stones and then launched to poison the enemy in a rather fancy way to throw a rock. Orpiment is known to give off a strong garlic smell due to its arsenic content, and may crumble into dangerous powder when exposed to light. The mineral was used as a primary component of ochre paint, and likely poisoned many of the artists who used it.
I'll bet that ol' Dizzy Dick has seen something like this. I think that he has messed around a lot of minerals and such before.
Let's have some more coffee out on the patio this morning. I have a little peach cake I'll share!