It seems too big. If you're determined to get a mirror, then an antique, rustic one that links with the mantel would look better--horizontal filling about 2/3 of mantel. Here are a couple from Etsy--not right size but style that would tie in better with stone and mantel--more affordable than CB2 and a lot more character.

Your mirror only seems to reflect the ceiling. What about a great piece of art instead? It should be horizontal though this one isn't. These are suggestions for bold, outdoors art work to bring out natural elements of stone and mantel.

Clouds Roll, Stretched Canvas Wall Art · More Info

"Gold Leaves." Original Artwork By Kanayo Ede · More Info

That is a beautiful wall No mirror I would put some pretty green plants

Mirror reflects the ceiling— not a good look. Art leaning or plants— that whole fireplace area is beautiful

Art over mantel and I would do 3 overlapping pieces of art and a couple objects. Gorgeous wall. This is just concept. You can select art and items that speak to you but keep the color palette white, black, grays with spots of color. Object should be organic in shape.

A good guideline is to keep a hanging piece no wider than the firebox opening and lower than the top of window frames nearby. If you don't lean it, then hang 5" above the mantel.

I don't think the mirror works - style or size-wise. I would opt for artwork to bring a bit of color to the room .... love the layout from decoenthusiaste above!

Another vote for no mirror. It's repeating the window and tv, and doesn't reflect anything interesting. A piece of art, or ironwork. Like an old rusty metal piece you can see through/not solid. Something woven, naturally artistic.

Your mirror looks good to me❣️You could secure it to the wall with double sided Alien tape: it holds up to 15 pounds.

Just for fun, my son demoed a smaller mirror vertically and horizontally. I do agree keeping the width to match the opening does look better! (Never realized!). I think agree the mirror looks blah, so will need to find some interesting art.

I added huge African basket and tried to layer some water painting just to get a feel (I know they are wrong size).

I do like the idea of some texture as someone suggested, much better than the mirror after all. It only showed our heads so it was creepy. Lol. I’ll keep experimenting! Thank you for tips/suggestions. You all have amazing design talents.

(And for true inspiration, here is the embarrassing BRFORE pix. I had mismatch junk all over the place , no concept of design amd too shy to ask for help.

That basket is great, Lisa. Go for it! You did a great job on brightening the room.

Just white washing stone really enhances and updates the whole look.

That's quite the transformation of that wall! It looks really nice! Glad you agree no mirror.

The basket looks good, as does the white washing.

Here are a couple inspirations. Seems a kind of minimalist look would be pretty against stone.

I voted to keep the mirror then read the comments, saw the great difference the art makes & the amazing update of your before & after on the fireplace & ceiling. Cancel my vote & go with the art!

You can place items you like. Just overlap for interesting depth.

Lisa J - you did a beautiful update on that fireplace wall! It’s lovely. 😄

Oh and I love the African basket. Play with some combinations with that. Love the texture and interest it brings.

It seems good to me. Check RH they have higher and lower mirrors over window trim. No any rules about width of fireplace opening as well.

I really like the choice of the fist mirror!! I thought it was the perfect size. I find most people get the scale wrong when hanging things over the mantle. They get it too small then start adding things because it looks skimpy. I say go for that lovely mirror and if you add anything else, keep it simple. The rock on that wall is very busy so keep your accessories simple but bold enough to stand out. For Christmas, you could hang a smaller wreath directly on top of that lovely mirror. Your first idea was correct!

Love the white washing! Totally agree with art vs a mirror in this case, and I like Flo's overlap suggesiton. Your ceiling looks just like what we have in our family room. White with white beams.

I was so nervous to paint the ceilings in our 1954 Arizona home. My designer sweet friend gently kept nudging us out of our comfort zone. Here is the mantle with a smaller Target mirror because I had a coupon for $40 and it was $60 shipped. Not sure yet, but have a few days to think it over. The hard part about the stone fireplace is the jagged rocks make it hard to hang anything. When I get some art work, I will continue to expedient with the ideas above.

Thank you all for sharing your creative talents to help us beautify our home.

(Sorry for all my typos! I wish I could Edit my posts but haven’t figured out If possible)

The size of that mirror is nice, but a piece of artwork that you love would be fab. i agree that the whitewashed stone and painted ceiling are very pretty.

When a mirror doesn't reflect anything pretty, it just leaves a big "blank" look. Use a black frame for 2-3 different sized black and white art and you will have a beautiful vignette over the mantel. You can add touches each season to bring a fresh note. Maybe a vase with some bittersweet for fall, holly sprigs with red berries at Christmas, etc. If you must do a mirror, then you must put a nice chandelier reflecting into it Black beaded one might work well.

Nova 18-Light Sputnik Chandelier · More Info

Oglesby 4-Light Chandelier, Washed Pine · More Info

Styling depends on what furnishings you plan for the room??

Wow, amazing transformation!!

Beautiful transformation!!

Agree with the others: a mirror is not adding much wow to the space. Since there's a window next to the fireplace, I'm not seeing a great need for a mirror. My vote also goes to original art. Splurge on something that makes your heart sing. Since you mentioned Arizona, the Arizona Artists Guild virtual exhibit might inspire. You'll probably find emerging local artists on Etsy as well. If your heart is set on a mantel mirror, do consider one with vintage appeal as @housegal200 suggested. I'd want to juxtapose the minimal setting with a frame with some texture or dimension. Perhaps even a convex mirror? Painter's tape can help you visualize dimensions. Maybe brick clips or brick hangers would help with the mirror hanging? Another option for dimensional art, for example, is a ceiling track system.

Btw, I don't find your before pic embarrassing. The wood ceiling and original stone just offered a different vibe than the whitewashed. Both are lovely in their own way.

It’s a much better mirror, size wise and just play around with different items to create a layered look.

How about this concept:

Hang your artwork or mirror from the ceiling with chains. In this case I chose a tiffany window panel. A Custom 3-Fold Fireplace Screen and matching fireplace tools can help provide balance allowing you to hang a piece that is wider than the fireplace opening.

Unless you actually need the mirror here for functional purposes, I would replace it with some artwork.