Ive had this happen before and messing with it a bit fixed it but now its pretty much stuck like this.
Replacing it by copy and pasting mats from G8 base work a little but, leave a black ring around the Iris.
Trying to replace it with any eye texture other than that makes it black. I can make the entire eye a nice shade of silk or metal but any eye texture turns it black.
Yeah, I would never have thought to do that. The figure was lit, why wouldn't the eye receive light as well? But HDRi's can behave really strangely though so I'm not surprised.