Any natural stone material can exhibit largely superficial - if that is the case - cracks like this one. The heat from a fire may or may not have anything to do with it. A gas fireplace would be even less likely to reach temperatures high enough to crack a surround unless there was already a flaw in the stone. The danger is that repeated expansion and contraction associated with fires will cause the crack to enlarge. In a brand new house and granite installation, replacement is probably the best option.

If it continues to grow you have a problem on the other hand it may be a natural flaw in the stone.

Thank you both for the comments. Akamainegrower I wouldn't call it superficial, it is very noticeable, and I can feel it, and it wasn't there before yesterday. On the bottom I can feel that it goes almost all the way through the stone, and vertically it goes completely from top to bottom.

If it can be repaired I don't have a problem with that, I just don't want it to continue to crack and be afraid to use the fireplace going forward.

Sandy: with your further description of the crack, especially the part about its depth near the bottom, I would really insist upon replacement. Although it may have possibly started as one, this is no superficial crack. It is long and deep. Repair using an epoxy type filler may be possible, but I wouldn't be inclined to trust it with a crack that goes all the way through the thickness of the stone. A good deal will depend on what sort of warranty came with the installation. I'd also suggest some kind of heat shield to protect the surround. The manufacturer of your fireplace may sell them or be able to suggest one.

I did a quick Google search and found this:

"Granite is a very dense material, so it can stay quite cold to the touch, if a sudden change in temperature occurs in a localized area cracking can occur. Granite can withstand some exposure to heat but placing hot pots direct from the stove or oven is not recommended. Heat generated through large windows can also cause cracking especially in Black granites, which is very dense."

http://www.heritagestone.com.au/granite.html

Thermal expansion and contraction which is exacerbated by enclosed moisture and high heat cause's stone and quartz to crack. It is incorrect to believe a "gas fireplace would be even less likely to reach temperatures high enough to crack a surround". Gas units shocked the stone instantaneously rather than gradually changing the temperature like wood burning masonry units. However, wood burning units will crack the stone if the user inserts too many logs into the firebox. Some gas units designed for commercial establishments have been specified for use in residential settings with btu (British Thermal Units) ranges of 60K and up. Googling this issue illustrates many people are experiencing this phenomenon even with low btu gas fireplaces where cracks developed at the four points of the metal housing. The only justifiable reason for these cracks is thermal expansion and contraction via high temperatures and prolonged fireplace use (hours). It is disappointing people become a victim of basic physics because they want a seamless installation shown on the cover of Architectural Digest. Sometimes you need to heed the advice of the stone expert rather than the architect / designer. Post date: 11/15/16

Thanks for your reply Pataya Flooring and Stone Supply, LLC. No one warned us about any issues with using granite around the fireplace. The granite company that installed the stone came and repaired it. They felt it was due to the settling in the house, which made sense as there is also a hairline crack in the upstairs ceiling that is above the fire place.

We have run into the exact same problem. We have a newly remodeled fireplace and used the Kingsman ZRB46 gas fire place insert and a ceiling to floor marble slab surrounding it. Our contractor and stone fabricator assured us this would look striking and there were no foreseeable problems. Our marble splintered immediately after first use in several places and has since been torn out. The contractor and fabricator believed its from the heat expansion of the fireplace and with the correct modifications and using a harder stone, that we can still retain the striking seamless look we were after. My doubts are high on this. Can you suggest a better idea to surround this type fireplace? I don't want to waste more time and money. Thank you for your help.

I am an interior designer and have been schooled from my granite/quartz provider that a heat barrier of some sort is always required between the firebox and the solid surface used as a surround. The stone acts as a direct conduit for the heat transferring from the box to the stone. The rapid temp changes cause the cracking.

Sandy I'm sorry to learn about your other cause. It's also good to know. My description is from known failure's and your's clearly is another issue leading to your foundation.

Hi Sandy. I have the same issue re granite & fireplace - exact same crack line. Do you mind me asking how the company repaired the crack? TIA for help.

Here is crack...

They covered the floors and walls around the fireplace with cloth to protect them, and used a polishing machine with water to fix it. It took a couple of hours to do. You can't see it but you can feel a little bump where it was. Hope you get your fixed.

Thanks Sandy - so frustrating but hoping with your input I can get sorted!

Hope it works out for you.

Im interested to see this post and im getting worried as Ive really set my heart on a granite slab around our cassette stove fireplace? We have been advised that it will have to be fitted in 2 parts as too big...would this sort of help if it has an expansion gap etc. I really dont want to have something put up for it to have to come down again. JVA...how did they fix your slab to the wall?