Why did my black granite Counter Top discolor?


I just had black galaxy granite installed and am wondering if it's been doctored. The reason is that a repair guy had to come out to polish the seam (which was full of chips on the edge) and when he polished it the area is very noticeably gray and not black anymore. Then he mentioned that it's impossible to polish it to match the color properly since the black granites are all dyed at the time they are created. Could I have gotten a dyed low quality black galaxy slab? I tried the lemon test, but not sure exactly what I'm looking for. When it says look for "black spots" what does that mean? Does that mean when you look through the lemon drop if there are spots that look blacker when wet? Because I do see that and I even see it when wiping the countertop with water. You can see noticeable black patches where I wiped but they dry up quickly and then it returns to normal. Any advice would be greatly appreciated!


ANSWER - Many granite slabs are treated with resin color enhancers to make the granite slab look better.

If the granite slab's polished surface was adjusted then the fabricator should have repaired it so it matched the rest of the counter top.  That will require him to use an enhancer too.  This is difficult for the fabricator because they might not know what the stone processor used originally.

Using an enhancer of some slabs of stone doesn't necessarily make them low quality.  Today it is more common to see this practice.

The fact that the granite slab gets dark when subjected to water suggests that it absorbs moisture, indicating that it has some degree of porosity.  There are stones that are sold as granite, but they are not true granite.   These are considered commercial granite and they can be sold as granite.

The lemon test is normally done to verify how resistant the stone is to acid etching.  If it leaves a mark that you can't remove then it is acid sensitive.  Granite stones should not be acid sensitive.

4 thoughts on “Why did my black granite Counter Top discolor?

  1. Michele says:

    Hello I have black granite which I always washed with plain water and my cleaners started using method granite cleaner and method brand bathroom cleaner on my granite floors. The other colors were uneffected but the black granite turned to what I call whitish (I suppose grey but it looks more like spotted white mixed with darker area beneath). I thought it was from
    The chemicals in the Method brand cleaners but now I think that the granite was dyed? This happened suddenly and the areas that only water have been used for 12 years were uneffected (walls)

    • Donato Pompo says:

      Many granite natural stone or stone sold as granite that might not be a true granite are often enhanced with special stains or sealers. Some solvents can cause the surface of the granite to discolor.

      True granite is typically chemical resistant, but some stones can etch from acidic cleaners.

      You can either hire a professional stone restoration company to refinish the stone, or you can try to touch it up with some of the stone enhancers sold at the home centers or at stone suppliers.

  2. Krista Gilmore says:

    Hello Mr. Pompo,
    I think I may be a victim of doctored black galaxy granite, too. I have blotchy spots near the sink area & had a company come take a look at it. After doing some research I don’t think that gentleman knows all he should about black galaxy granite either. He did say he thinks it is doctored but then told me it needs to be sealed. I read that black galaxy granite is not supposed to be sealed. I have been trying to find more info on this granite, or doctored granite so I decided to pose this question to you. What in the world can I do if this is doctored black galaxy granite? Is replacing it the only option? I ordered a bottle of MEK to test it so I’m not 100% certain this is doctored but I am beginning to believe it is. Is there any way to salvage doctored black galaxy granite? Any info you can provide is most appreciated. I am more than willing to do more research but information is hard to find on this subject. Thank you!

  3. Donato Pompo says:

    It is not uncommon today to have granite stones and other stones to be enhanced with a type of sealer that brings out the colors in the stone. Sometimes a solvent of one type or another can cause the sealant to become blotchy. The beauty of natural stone is that it normally can be refinished and polished to be like new. You should hire an experienced professional stone restoration company to evaluate it and determine how best to repair the undesirable stone conditions.

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