A picture would be very helpful to see what you are seeing.
Where exactly is the broken rock? How broken is it, a crack, a chip, a split, crumbling? Is there mortar involved? And why did it crack is probably the most important question?
Sorry to ask so many questions, but the integrity of the fireplace is important so you do not burn your house down.
Can you post a picture of your broken rock situation. Knowing the the size and placement of the broken break can help us offer solutions. If it’s a cosmetic or structural repair or exposure to heat may indicate different needs.
Likely can use different metods depending on the size of the problem and if you have a replacement rock or if the rock can be epoxied together and reattached. A pic would be very helpful.
Cement or mortar. Mix a small amount and attach broken piece or fill a crack with it and wipe the surface after a few minutes and before the mortar sets.
A picture would be very helpful to see what you are seeing.
Where exactly is the broken rock? How broken is it, a crack, a chip, a split, crumbling? Is there mortar involved? And why did it crack is probably the most important question?
Sorry to ask so many questions, but the integrity of the fireplace is important so you do not burn your house down.
If you still have the broken piece, you should be able to reattach it with an epoxy. If it's missing, you have a bigger job. Here's a link:
https://www.doityourself.com/stry/how-to-repair-a-damaged-stone-fireplace-surround
You will most likely need to chisel out the broken rock and surrounding mortar then replace with rock(s) that will fit in the space.
Here is a thread on Hometalk that should help. You can reattach using mortar if you still have the rock.
https://www.hometalk.com/diy/living-room/fireplaces-mantels/q-how-or-what-can-i-use-to-reattach-or-fix-stone-on-fireplace-44233130
How or what can I use to reattach stones to a fireplace surround?
Can you post a picture of your broken rock situation. Knowing the the size and placement of the broken break can help us offer solutions. If it’s a cosmetic or structural repair or exposure to heat may indicate different needs.
here is info for you Dianne
https://love.firerock.us/blog/repairing-broken-fireplace-components
Likely can use different metods depending on the size of the problem and if you have a replacement rock or if the rock can be epoxied together and reattached. A pic would be very helpful.
Janice is right the fix will depend on how bad the problem is to begin with.
My dad had a rock surround on his fire place and it really dates the entire living room.
How to Update a Rock Fireplace By Using Painthttps://www.ehow.com/how_12343229_update-rock-fireplace-using-paint.html
30 Ways to Refresh Your Fireplace on Any Budgethttps://www.hgtv.com/design/remodel/interior-remodel/ways-to-refresh-your-fireplace-on-any-budget-pictures
You should be able to clean off the old cement and then re cement the rock right in
Cement or mortar. Mix a small amount and attach broken piece or fill a crack with it and wipe the surface after a few minutes and before the mortar sets.
Is it outside or inside? I found this for an outside fireplace, which might help: https://www.youtube.com/watch?v=oaxMJ-3h8As
can you share a photo? How easy the fix is would depend on where and how it was broken.
I would mix some cement and fill the crack or create the broken part of the stone. You may need to paint it to match the rest of the stone.