Chickens eating saltpeter

[Altairsky]

Just figured out why my chickens finds so entertaining hanging out in my patio. They eat the saltpeter coming out of my patio's marble slabs.
Anyone had their chickens eat this delicacy?

 

[Debbie292d]

Do you mean the salt used to melt ice? Saltpeter isn't used in marble slabs, at least not here in the States.

Regardless, as you probably already know, that's not good for them, as it's way too much sodium for them. Maybe you could rinse it off?