Limestone hearth - crack or vein?

[JFritch]

We purchased a 300 lb (2" thick, 18" deep, 6.5 ft long) hearth made from limestone (Indiana Chestnut). We took it off the pallet to dry lay it and center it (before we wet laid it) and found what we think is a hairline crack/defect in the stone - 100% front to back across the stone and 80% of the way through the stone top to bottom (see attached pictures). The supplier claims that it is simply a vein and there is nothing wrong with the stone. Thoughts?

Thanks! JFritch

 

[bholler]

I think if that was a crack it would be in 2 pieces but i don't know can you feel it? or does a knife drug across it sound different at the line?

 

[ian105]

Just curious---whats the approx cost for something like this. Really want a slab of stone for my pellet stove pad vs doing something out of say granite tile. I think it just looks more "finished" and part of the house when its a slab. No technical reason other than looks as its going directly on top a concrete floor.

 

[fraxinus]

I would say it's defintely crack. I also wonder how suitable limestone is for a hearth. Limestone is a porous rock which can absorb moisture both from the air and, especially, if liquid is spilled on it. The constant temperature fluctuation a hearth has to deal with may be a problem for this type of sedimentary stone. I think would certainly want some kind of warranty from the seller.

 

[BobUrban]

a warranty would be nice for peace of mind(sort of) but once set it would be a serious hassle to remove and replace.

Is "perfect" the goal? Or a rustic natural stone look? For me I would set it and forget it with the line/crack just adding character but if that is not the look you are after I would replace it now. You can always seal the stone if porosity is a concern - I do think a stone like that would stain more easily than other, less porous rock if not sealed but again, that would just be character for my hearth - other settings stains may be an eye sore.

 

[firefighterjake]

Not sure if this comment is relevant or not . . . but I will say my slab of soapstone that I have on top of my stove has a very similar looking crack . . . and I do consider it a crack -- not a vein -- as you can feel the crack with your finger nail as you glide it along the surface . . . but it has also remained that way now for well over a year without cracking in two. It does not however support anything as heavy as a woodstove . . . only a trivet and steamer.

 

[JFritch]

It is a raised hearth - 12" off the ground on a well reinforced box (Durock, etc) to align to the bottom of a raise wood burning fireplace. Now that we have been researching on this issue, probably not the best choice we could have made for a material - it looks nice but we don't care for the crack.

We ran a knife across it - we maybe can feel something near the back of the stone but nothing on most of the surface - but then again, can you really feel a hairline crack? Perfect isn't the goal - our concern is lifting it off to wet lay it and then have the hairline crack turn into a full crack and damaging our tile floor when it breaks in two. I'm reading that limestone is very porous but I'm not seeing anything on hairline cracks - we will talk to the supplier again.

 

[Dakotas Dad]

Stone is always sold as a "natural product" cracks, veins, color, etc is never warranteed. The weight of the stove is sort of a non issue as long as the slab is properly bedded, it can't move. An issue I see is if this instal will require much stove movement, for cleaning etc, because that is a pretty soft stone.. (also, if I might add, a good looking one)

 

[Tenn Dave]

Sure looks like a crack to me. If this is something that will bother you, I would bring it back. You should be 100% happy with your purchase.

 

[homebrewz]

Can you look at it up close with a hand lens or magnifying glass? If you see a void, it's probably a crack. If it is filled with material, possibly of a crystalline nature, then it's a vein.. which is essentially a solutionally widened crack filled with hydrothermally deposited minerals.

Limestone has varying degrees of porosity. I happen to have a sample of Indiana limestone here as a stone mason friend of mine has been working with it. It looks much more porous then the limestones we have around here.

 

[JFritch]

Homebrewz - excellent tip to use a magnifying glass to look at it - definitely a vein filled in over time - boy do I feel better now. And darn - I'm an engineer - why didn't I think of using a magnifying glass! Thanks everyone for the help! I will be installing it this weekend.

 

[homebrewz]

Homebrewz - excellent tip to use a magnifying glass to look at it - definitely a vein filled in over time - boy do I feel better now. And darn - I'm an engineer - why didn't I think of using a magnifying glass! Thanks everyone for the help! I will be installing it this weekend.

I went to school for geology. A hand lens is standard equipment when looking at rocks.
Glad I could help!