Why does my stone discolor?

An elegant stone floor makes a sophisticated statement in any home or business. But what happens if your beautiful floor begins to turn yellow? Unfortunately, this problem is not uncommon.

The most common culprit for white marble turning yellow is iron, which can be found in many natural stones. When exposed to water, acids or bleach, the iron in the stone will begin to oxidize and turn it yellow. In extreme circumstances, the marble can turn a brown color, akin to what happens to a piece of iron left out in the rain. To find out if your marble contains iron, you can have your stone tested by a lab.

Oxidation is accelerated when marble is saturated with water. If you’ve had a pipe burst or excessive water has been used on the marble floor, have your water tested for iron, especially if you’ll be cleaning with it. It’s also a good idea to test the marble for moisture if it has been soaked with water.

If oxidation is indeed your issue, preparing and applying a poultice solution may rid the yellowing from the marble in some cases. There are also some new products that are aimed at removing iron oxidation. Consult with your stone restoration contractor for poultice mixtures or other products that may work best for your situation.

Wear and tear can also cause yellowing of white marble. As the polished surface wears away, trapped dirt in the marble’s pores can give the stone a yellow appearance.

Using dirty mops allows dirt to accumulate and remain even after cleaning, resulting in a dingy, yellow looking floor. This type of yellowing may possibly be removed with a professional cleaning with a heavy-duty stone cleaner.

When waxes are used on marble, the waxes themselves can build up and turn yellow, leaving your gorgeous white marble looking aged and yellowed. In this case, the floor will need to be stripped to attempt to remove the color.

Some stone floors are polished using the process of crystallization. If your marble contains any moisture when this type of polishing occurs, the stone will begin to yellow. This can sometimes be reversed with a powder marble polish and if not, the floor will need to be honed by your stone and tile care professional. See Dr. Fred Heuston's video on crystallization here!


Installers who rush or do not have the proper education will sometimes use the improper fasteners when installing the substrate prior to installing your new marble floor. They will use nails instead of the proper backerboard screws. This can cause rust from the nails to penetrate through the more of your stone and discolor your stone.


If your home is on a crawl space, you may need to check your moisture levels. An improper moisture barrier will expose your entire home to unhealthy and moist air. You want to ensure that your moisture barrier meets code with a minimum (never hurts to go thicker) of a 6 mil thick plastic sheeting that properly covers the entire crawl space and all of the seams to the plastic over lap and are sealed with a moisture proof tape.

As the seasons change, so does the amount of sun beaming through your windows and bringing its UV rays into your home and onto your countertops. Unfortunately, prolonged direct sunlight can cause damage, manifesting as fading or darkening on some granite countertops.

Natural stone treated with resins are vulnerable to damage from direct sunlight. Applying resin to natural stone is now becoming commonplace because it strengthens the slab, allowing companies to eliminate waste from breakage during manufacturing and shipping.

Keep in mind that engineered stone, or quartz surfaces, as they are often called, are bonded with resins, making them susceptible to this same sort of sun damage as well.

Your natural stone countertops are an investment and you want to keep them looking beautiful for years to come. You can always check with your fabricator to see if your stone has been treated with resins, but it's always a good idea to play it safe. Taking some simple precautions to minimize the time your granite, marble or other stone countertops will be exposed to direct sunlight will go a long way. Simply closing the blinds during peak sunlight hours can be enough to prevent the damage.

For outdoor kitchens, consider a cover for your stone countertops when they are not in use.  There are also some new innovative products on the market that can be applied to stone that act as a sunscreen to block UV rays.

The good news is that natural stone that has faded by sunlight can be repaired. Stone that is not resined can be honed and re-polished by a professional restoration company to bring it back to life.  If it is resined, there are chemical dyes that can be applied to return the stone's color.

If you have questions or concerns about your natural stone fading or darkening, contact us today.