We just had a thermal bluestone patio installed and the stone, after a few months, has weirdly begun to chip (spall?) on its own and turn colors, like black and rust brown. Is this normal for thermal bluestone? When we were house-hunting, we had seen two homes that had thermal bluestone patios and thought it looked so nice that we would install one ourselves at whatever house we ended up with. Both those homes were at least a few years old and their thermal bluestone pieces seemed to have weathered well, looking smooth and dark gray, almost like granite. When we got our thermal pieces, most of them weren't as dark and had more color variation (all still bluish, though) - not sure if that means anything. All we know is that after a few months, the surface of some of our thermal bluestones are pock-marked (revealing a rust-colored pebbly interior) when they were mostly smooth before - some even have a golf ball size chunk missing now - and some pieces have discolored, as you can see from the pictures below. The last picture shows the general color variation in a good section of the patio (you can see a few of the darker pieces that look like the ones we saw at the other houses - two on the left, one at the top and one long one on the right). Does anyone have any idea what could be causing the color changes and spalling? We're worried that these problems will get worse and that all the stones will turn black/brown and/or continue to spall. We didn't expect all these problems with thermal bluestone, especially for the extra money.

From my preliminary research on bluestone, i guess there are different density grades depending on the batch that was quarried. This combined with the freeze thaw cycles in the NE seem to be the possible culprit. The stone yards have no clue when I address this issue to them and they have no clue what type/quality of bluestone they are selling. So my multi thousand dollar walkway looks like crap and I have to see it several times a day. I don't know if replacing some of the stones is worth the time and money if this will only continue to happen again and I am not sure how to purchase/specify stone that is less likely for this to happen based on the lack of knowledge of most salesmen. If i had to do it over again, I would have used a bluestone-like concrete paver.

My contractor was also perplexed and was giving me the old "stone is a natural substance with imperfections" BS. After his 2 failed attempts at making the appearance acceptable (scraping and burnishing), he is still willing to work with me on this problem up to and including some stone replacement....but i need to know if there IS? a solution?