While stains and etching are two of the biggest concerns in using natural stone in the home, one frequently overlooked problem that is a real issue for many homeowners is yellowing of white stones. Marbles such as Bianco Carrara, Calacata, and Bianco Venetino all start out with white backgrounds and some degree of gray or gold veining. Over time, however, these stones can take on a yellow to orange cast or hue that can ruin the look of the stone for the users.
There are essentially two causes of yellowing in white stones. The first is simply a top layer of grime and staining. If the floors have been waxed such as Tuscan finished stones, the wax may also yellow as it absorbs some dirt from the surrounding area.
If the yellowing is caused by dirt, the stone can be cleaned either with poultices, or by grinding down the surface and refinishing the stone. You can test to see if the issue is grime by using a deep cleaner meant for marble on a small area of the stone, or by using a stone poultice to see if it lifts the yellow color.
The second cause of yellowing is the oxidation of the stone. Most white stones such as Carrara marble contain large amounts of iron. Sometimes this iron can oxidize or begin to rust, particularly if the stone is used in a wet area such as a shower or entryway. If the stone begins to rust, this cannot be altered, as the iron goes right through the stone and does not sit on the surface where it can be ground or buffed away.
Not every white stone will oxidize or rust over time, but if the stones are meant to be used in an area with hard water, which could speed up the oxidation process, it may be better to choose a white quartzite such as Ajax or another type of stone altogether to avoid the issue.