Deliquescence!

Apparently these are Hare's-foot Inkcaps, delicate & short-lived, the fruit bodied lasting only a few hours before dissolving into a black ink - a process called deliquescence.
I have seen them before (they are widespread) but never tried to identify them, but an app on my phone is great at identification & these looked pretty at lunchtime today along the boardwalk at The Argory.