Call me crazy but I get a strong modern feel from that stone arrangement. I could see that looking really interesting if painted either gray or white, with an alternating wall color (gray stone, white walls, or white stone, gray walls).

Oh boy!

That fireplace is awesome. It is unusual and unique. Of course I am not a cookie cutter/follow the leader type of person. I really could see it in a modern or lodge style of room. Please no paint on stone or brick!

Rip it out! Also the paneled walls.

If the house is in a part of the country where slate was quarried, what you have is a great example of indigenous architecture utilizing local materials built by local craftsmen. It is imposing and unusual and certainly not to everyone's taste, but imho it would be a shame to paint it or tear it out to be replaced by something that looks like a million other fireplaces. "Redoing" houses to make them conform to stereotypical notions of what a house should look like loses everything that is valuable in local traditions and regional approaches to building styles and materials used.

If possible test paints on the actual wall, we have wall-o-stone as well and getting a color that played nicely took a few tries. Straight up gray may be too cold.

If you think it is horrible, you take a cold chisel and a 3-pound sledge hammer, and starting at the top, try to dislodge the stones from the wall. What does it look like from the outside and on the roof?

I can't think of anything more dangerous to your house and to yourself than whaling away at this chimney with chisel and hammer. When broken, slate produces jagged and extremely sharp shards. The stones are also massive and heavy which can do a great deal of damage if they unexpectedly fall. Removing any sort of chimney involves risk, but this one weighs a great many tons and is a far cry from dealing with bricks that can be easily handled. You're also not going to be "dislodging stones from the wall". The stones and very large quantities of mortar are the wall. Should you decide that the chimney must go, you need to hire people who have the equipment and expertise to do it safely. This is no DIY project.

I think removing would be more expensive and a hassle than other options. If you really want to change the look entirely, get someone in to see if it could be stucco'd over and made a neutral color/appearance. If you plan to use it, I think a fireplace insert (likely would require new chimney inside/through the existing) would be far more effective heat-wise. You probably would not gain much heat from the current installation unless sitting right in front of it.

Personally I'd probably learn to live with the existing look as pretty unique, and see about how the rest of the room could be made to work with it. If you do cover over existing with stucco or otherwise, make sure to take photos so that memory will be retained of what's under there.

What makes you think the stones are massive and heavy, akamainegrower? To me, it looks like relatively small pieces embedded in concrete. The fireplace box was created from bricks. It looks to me like the slate is just a facing.

graywings123: Slate is a dense stone that has considerable weight per volume. Further, if you'll look at the first photo showing the fireplace opening you will see that the stones are not small pieces or "just facing". They are laid up with a good deal of the stone volume in a horizontal plane. Not to mention the fact that there are also numerous large stones invisible from the front because they are completely hidden. This is not at all what we find if stone was used as a facing. Let's also hope that the builders used the proper material, namely mortar, not concrete.

Judging from the firebox, the chimney is quite old. Have a CSIA certified sweep check it out. The liner is probably shot if it has one. It could be a good candidate for a gas insert with modern trim. If you decide to keep it, I'd suggest a slab of slate on top of the current hearth extension. Maybe get some 2" verticals, with the hearth extension protruding over them an inch.

If you're going to get rid of the slate, you cover it with tile board, then tile or put a different stone on. Adding weight to this could be an issue. It doesn't look like the slate was part of the original construction.