Cat digging in fireplace, eating charcoal/ash

One of my cats has a fetish with the fireplace (not lit of course) and loves to dig in the bottom under the grate. It's a gas fireplace, so the stuff that is under there isn't wood ash, but more like soot. One thing is it makes a mess (all over his paws), but secondly I realized that he is eating the black stuff occasionally. I recall reading a long time ago that cats will do this if they are lacking something in their diet? He's otherwise healthy - just wondering if anyone else has experienced this and if it's a health thing or more of a behavioral issue. Appreciate any advice. Thanks.

Please get your kitty to the vet and have bloodwork done on him. Cats eating ash are generally suffering from a health issue like anemia

I agree. Take your kitty to the vet. I just lost my Peace a few weeks ago and one of the things he started doing was licking the soot off the woodstove.

Thanks much, appreciate your advice. Off to the vet we go.

Can you secure a gate/grate (whatever that's called..) over the front of it so that he cannot get in there at all?

I had a Cat do that years ago and it was Anemia. You need to go to the Vet.

We generally have a wooden screen over the whole thing but have left it off during the winter when we light the fireplace. Sometimes he'll get back there and "dig"...I honestly think it is more of wanting to get back underneath to "find" things that he might hear up in the chimney. He doesn't eat the stuff often, it seems like it's more to play with it (he is one of those that gets bored easily and likes to be "entertained"). He is an indoor only cat and is of course fascinated with anything that smells like the outside. We'll be putting the screen back over it soon and we secure it the best we can (we actually have it wired so he won't knock it over - sometimes the other cats will go back there to play hide and go seek"). I'm wondering it if would stop if we put a piece of wood over the front so he couldn't get to it. If he couldn't and stopped trying it would probably indicate it was more of a playing (digging) thing than an "eating" thing. I bet a call to the vet would solve it all.

Keep him OUT of the fireplace - put up a secure screen or glass screen. Eating the charcoal/dust could make him very sick.