Bleach Damaged Marble Floor
I bleached my black marble floors and it damaged them. Also, my black granite counters look very dull and have a small spot that needs repair from a bottle of grout cleaner that left a ring around its edge.
Yes, using bleach for cleaning marble (or any stone really) is not good. It can be used sparingly in certain situations in a very very dilute solution, but more often than not people get the mix wrong and etch their marble. So, it's best just not to use it.
Etching is corrosion that eats away at the marble, which will cause dull and light colored spots. Bleach, ammonia, vinegar and most common brand-name cleaning products will do this.
Etching can be fixed, but it depends on how large an area. If your whole floor is etched, then you may need to hire a marble maintenance professional to re-surface your floor.
If a small area (6x6 feet or less), you can do it yourself using ETCH REMOVER / Marble Polishing product
, which will restore the shine and color.
The black granite is another matter. Granite does not etch like marble except in extreme and rare cases, so the grout cleaner should not have left an etch mark... or rather the etch mark is not in the granite itself.
It could be a couple things. Unfortunately, there is a bit of fraud occurring with some black granites that have been "doctored" with surface coloring to make them more "black." This surface coloring can etch and is often a tell tale sign of doctoring. But it also could be a sealer or resin that has etched.
The FORENSICS Granite Test Kit
will tell you what is happening with your granite so you can find a solution.